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6000540270 



hi. 



REPORT 






RESULTS OBTAINED B¥ THE USE 



THE MICROSCOPE, 



HUMAN ANATOMY AND PHYSIOLOGY; 



BY JAMBS PAGET, 




LONDON : 
JOHN CHURCHILL, PRINCES STREET, SOHO. 



1011 



Arif.AND, PRINTER, RARTHOLOM B«V CL08B. 




Thb deaign of the present Report, of wliioh tlie greater part has been alread 
exteneirely circukted in the Ttritieh and Foreign Medicnl Review for Jul 
last, is to bring together, in the briefest possible space, the principal conclueioD 
regarding the structure and the functions of the several tissues of the humai 
hodj which have been rendered certain or most probable by microscopic ini'ei 
tigation. The task will, It is hoped, be deemed worthy of the labour which ha: 
been bestowed upon it ; for in no department of medical science has there heeti 
BO great an addition of facts In the last ten years as in minute anatoin; ; Hnd in 
none has the access to knowledge been more difficult. The greater part of the 
original records of microscopic anatomy are scattered through a multitude of 
monographs, brief dissertations, and essays in the foreign Journals, to which 
few can refer; and in our own language there is no work which affords an ade- 
quate notion of their contents. In France, Holland, and Italy there is thfl 
same defect ; and even in Germany it existed till, very recently, the systems of: 
general anatomy of Henle,< nnd Bruns" appeared. 

The writer has endeavoured to keep within the strict limits of the oMce he 
has assumed ; he has rarely done more than report what has been already puh- 
llahed ; but thitt he might report It accurately and Impartially he has been care- , 
ful to draw his materials froni none but their originiil sources. I 

Some of the numerous reference notes may seem superfluous ; but they are i 
iniierted in the belief that with tlieir aid it will not be difficult for any one who I 
has access to the works quoted to fill up the outline of knowledge which the 1 
text affords. By the aid of some, interesting histories of discovery may be I 
traced} by others, facts may be found which, though they now seem unim 
tant and are, for brevity's sake, omitted, may hereafter become valuable; bf J 
means of others again, llie description of the structure of particular organs, and 
the details of the facts which are related In general terms In the text, may be % 
at once referred to. 



' Allgenielne Anatoniie, von J. Uenle — Le[pzif[, IS-Uiheiiig the 6tb volume of the ] 
new German edition of SomniDring'g Anatonnle. The Report was nearly completed when 
this admirable wotIc onlTed In England : but the numeTOUH Teferenc^s nuade lo it will anf- | 
Bclvntlj prove of how mach avail It bns been for addition and condtmalion to wbat liad 
been wrtlleu. 

' Lehrbnch der allRcmetnen Anafamie Jes Merischen, von Victor Drnn', — ^Braun- 
•rhtelR, 1841. Hvo, 



REPORT, 8iC. 



nary cellii augge^rat 



The fnct of the one origin of all the tisEuea from primury c< 
the tnuet natural arrangement of them tiiuet be that in which tliey itre placed i 
a succession corresponding to the degrees and modes in wliicli, in their perfec 
condition, they severally retain or deviate from the primary form. And allhougi 
from the imperfection of the knowledge liitherto attained, such an arrangement 
cannot yet be certainly and completely ealablisheil, there are sufficient advan- 
tages in even a partial adoption of it to warrant its employment on the present 
occasion, with only such modifications as the physiological relations of certain 
parts seem, in some instances, to render more convenient than a strict adherence 
to system. 

DEVELOPMENT OP CELLS. 

The discovery of the laws of development of and through wlls, the greatest 
achievement of the microscope, is due to Schlciden' and Schwann'. The formec 
determined it in the vegetable, the latter in the animal, tissueK. Hypotheses of > 
cellular development, which in some respects came very near the truth, ha^ 
been formed by Heusinger,' Rnspail,* and Dutrochet;' and several of the facts , 
of the structure of cells had oeen disceroed by Robert Brown, Purkinje, 
Valentin, and others; but the facts aod their explanation bad never beon 
combined till the time of Schleiden and Schwann. Since the publication of 
their works, many facts have been adduced which show that the law, though iti 
general truth is confirmed, must, at least in its application to animal develop- ' 
ment, be modified ; but the changes to be introduced are as yet so uncertain, ', 
that, for present use, it seems best to adopt the original system, and merely to ''. 
append to it the tacts by which it may hereafter be altered.^ 

A Primary Cell, or as it is sometimes called, a nucleated or elementary cell, is 1 
a minutK vesicle, usually of a spheroidal or oval form, composed of a fine trnnk^ 4 
parent membrane, containiog au albuminous, gelatinous, oily, granular, 
other fluid, and having on its wall, or in its interior, a small body called tfae I 
nucleus or cytobUit, which, again, commonly contains one or more dark round. I 
spots, oucleuli, or corpuscles. Such cells are found either persistently or teu 
porarily, lis one of the forms passed through in their development, in all, i 
nearly all, organized tissues, wnether animal or vegetable, normal or morbij, I 
Wliaterer be the tissue to be developed, the first periods of its development 1 

' BfitiBgetiir Phylogenesis.— MUUer'sArcbiv, 1838. 

' Mikioitkaplache Uulersucbunf^n liber die L'eberninstimmung in dei Struktnr uod I 
ilem Wacbstliuni der Tbiere unit i'Bstizen. Bsrlln, 1839. I 

There ia an encellent aunlysis of these two works in the Brilish unil Foreign Medical I 
Ruview, vol. ix. 

' 8y8lBin der HUlologie, 1828, 

* NouT. Sysl. lie Chimie orgnnique. 

' Mvm. |u>ar neriir ik I'HIstoire dim Vegelnun et 

' The bdil accounts or these Inlet lovestlgatloDs afp given by H(^nle, in hl4 (iene»l J 

, tha Jnhresberichl ot ' ' 

' ifevotol to criticism of Henle'n obaervnlion?. 



seem to be aliDilar. I'bere is not first developed for eacli structure n peculiar 
form ; nur ia each produced first on n small scalo and then enlarged : but m all, 
the niulvcules are first arranged according to siuiiliirkwa; and tlienucleiited cell 
is the form up to which in every tiseue the prinniplc of development seeniB to 
tend, and from which it prucecds ina different direction for tiie further develup- 
ment of each. 

The material in which the cells are formed, and from which they derive their 
means of increase, is a structureless Siiid or soft eubstance, and is named cyto- 
blastenia. In the embryo it is thiit which has been called the formative, or 
primary, or indifferent Kubstauce: in the perfect animal it is the nutritive 
material efliitied from the blood-veseels into the intersticeB of already-existing 
tissues. When cells are formed und fixed in it, it is usually vailed intercellular 
substance, and may undergo changes whiuli contribute much to the character of 
the fully-developed tissue- 
In the development of all organized bodies, then, (here may be traced the 
development at primary cells ; and in that of some, the further development 
of various forms from or through such cells. 

The development of the cell is attained in different methods, but the chief 
of them may be reduced to two schemes. The first is that which is general ju 
plants, and which Schwann believed to be as common in the animal tissues. In 
It there are first produced in the cytoblastemn minute granules, perhaps simple 
cells. Around each one or more of these, an imperfect layer of substance 
gradually collects by a aort of coagulation of part of the cytoblastema, and this 
becomes gradually more dense till it forms a Sue membrane around the primary 
granule. The membrane continues to grow, and increases more in superficial 
extent than in thicknesa ; ao that after a time, n space is left between its inner 
surtace and the granule. The «pace is usually filled with fluid, and the granule 
remainsattnchea tosomepartof the membrane. In the next place, asecond mem- 
brane forms upon the first, and, enlarging at a much greater rate than the first 
does, separates from it, appearing at first ** like a watch-glass upon a natch," and 
then gradually rising and leaving a cavity which receives a fluid within it. 
Thus there is produced a membranous cell, inducing or bearing on. its wall a 
second much smaller cell, which again incloses, or bears on its wall, oueor more 
granules or cells. The largest and laat-formed is the primary celli the next the 
nucleui ! the third and smallest the nvcleolus. 

The other scheme of development, which is probably the most frequent in 
the animal tissues, differs chiedy in the mode of formation of the nucleus. I'his 
is not developed as a cell upon a granule, but, of the granules which are first 
formed in the cytoblastema, a few (rarely more than three) tullect, adhere 
together, and conjpoae a nucleus, in which one granule larger than the rest 
seems sometimes It) compose a nucleolus. On a nucleus thus formed, the cell 
develnpea itself in the manner already described; and, us the cell is developed, 
the granular character of the nucleus diminishes. The granules, which at first 
adhered very loosely, become inseparably united; and then, as if by the collec- 
tion of nil their solid material to their common circumference, they are gradually 
changed to a minute smoothly- walled vesicle filled with fluid. 

A scheme nearly analogouB to this is ohserted in the globules of the first 
milk, aud in some glohulea of pus and of inflammatory exudations, and several 
morbid products; in which a great number of granulea collect together, and 
tend, or attain, to the formation of a cell without any distinct nucleus. As in 
the preceding, the nucleus was formed without a distinct or previous nucleolus, 
to here, the development proceeds immediately by the aggregation of many 
similar granules to the furjoation of the cell. 

In whichever of these methods they be produced, the primary cells seem to 
possess the power of working upon their contents, upon each oilier, and upon 
the intercellular substance, and of effecting those diverse chemical and structural, 
ehangea by whii-h the infinite variety of organized lissues is produced. Accnn^H 



to thcBe chnnges Schwann divides all the ekmeatarj' forms of animal structu 
into five chief JiviBioiiB, ae follows : — 

In the firet, the form of the priomrj cells is nearly retained, nnd they eitl 
Aunt separately in a fluid, or are moveable on each other. Of this division i 
the blood-, lymph-, mucus-, and pus-corpuscles, and the endogenous cells 
certain glands, which, in their cumpletest state, are primary cells floating in 
fluid, and in which the changes after the formation of the celt are limited to tho 
of their size and form, and thoseof their contents, in which, culouring and oth 
matters, or new cells, are generated. 

In the second division, the primary cells are distinct, but the^ cohere bf the 
walls, and sometimes firmly enough to form a connected tissue, as in tl 
sererat varieties of cuticle, in pigment ■membranes, and in fat. The changes i 
form which some of the cells in this class of tissues undergo, though great) 
than those of the preceding class, arc simple. They assume a flattened, or n 
elongated, pyramidal, or conical form ; they throw out processes which becom 
cilite, or which, in some cases perhaps, as in certain pigment- eel Is, form canal 
of communication between the adjacent cdls; or they are merely cbaDged ii 
form by their mutual pressure, which makes them angular, as in tlie epidermii 
cells. Their contents also may be changed — becoming traoeparent, or bavin) 
granules formed in tbem. or disappearing and permitting the cell to dry. 

In tile first class, the fluid in which the cells float may be regarded as a per 
nianent cytoblastema: in the second, the cytoblastema seems to be entirely ol 
nearly consumed in the formation of cells; in some only of the tissues, a smnll 
quantity of it remains as a ttructurelessintcrcellular aubstance,holding thecelli 
together. In the third class, it becomes an important constituent of the tissue, 
The uells are nearly persistent in their primary form, but are separated from 
each other by the cytoblastema, which constitutes the chief mass of the tissu^ 
and with which the walls of the cells are ultimately fused. Of this class are tbs 
bones and cartilages, of which the peculiar corpuscles are the primary celli, 
and the basis or intercellular substance in which they lie is the former cyt<>> 
blastema. The chief differences in the cartilages depend on the relative quantity 
of the intercellular substance, and on its acquiring in its later development a 
finely fibrous structure. The canals of the bone-corpuscles either grow out,, 
from the aides of the cells, or are produced by spaces (intercellular passages) 
being left in the material deposited within the cells in the later period of their ' 
" development. 

The fourth class is eomponed of tissues which in their adult state consist of 
fibres ; the cella in which they originated having undergone an entire change 
in their appearance. In these, among which the chief examples are the varietiea 
of fibro-cellular tissue, each primary cell becomes elongated and spindle-shaped, ' 
and ilg extremities are drawn oat into fibres. These fibres sometimes branch, i 
and, at the last, they break up by splitting from the end towards the centre, \ 
where the several fissures meet, and form a bundle of fine filaments or tubulea, J 
In this way it is leliaTed that from each primarycell a fasciculus of the fliamentt I 
of fibro-cellular tissue is produced. 

The fifth and last class in Schwann's arrangement comprises the tissues which , 
are formed from cells whose cavities, as well as their walls, have become con- i 
necled together. In some of these the cells arrange themselves in rows, each I 
being fixed to the ends uf the two next to it; and the partitions which are at i 
first formed by their apposed extremities being absorbed, the cavities of all the i 
cells gradually merge into one. Thus, in the place of a row of primary cells,. | 
there is formed a single long cell, n secondary cell, whose wall is composed of -I 
theside walls of aaeries of primary cells. Suchare the nerve-fibre, the muscular f 
fibre, and the tubules of glands which bare simple membranous walls. The I 
secondary cell may grow like )t primary cell, and may form various substancei J 
in its interior; the peculiar nerve substance, and the muHcular fibrils, are sup- 1 
posed by Schwann to be deposited within the canities of such secondary cells ; J 



^fll 



and tbe icminal corpuscles, and the corpuBcles of Beveral otiier glands, luay be 
placed in the aanie Hat of secondary intra -cellular fomiationa. 

lu another cage belonging to this division, the cells, instead of arranging 
IhemsulveB in rows and coaleBcing end to end, lie scntteredat some dislance from 
each other, and, sending out proceBsei from their sides into the surrounding 
cjtoblastema, assume the shape of radiating cBTities. Their processes coalescing, 
they become a network of canals, in which the diSferences of caliber, which at 
first existed, arc gradually annulled. In this way, it is believed, the capillary 
blood-veseela are formed. 

Such was Schwann's system. Some facta are now to be mentioned, according 
to which it must be in a measure modified. In it the nucleus is supposed tu 
take no important part, except in being the necessary precedent of the cell ; when 
the adult state of the celt is attained, the nucleus is supposed to be absorbed, 
as it probably ia, in most instances, in the vegetable tissues. But it seems more 
probable, that in the production of uiany animal tissues, the nucleus has a 
more important part to perform. In Dr. Barry's system (examples of which 
will be noticed in their places), the nucleus has a greater share in development 
than the cell. Henle also states that the persistence and further deTelopmeDt 
of the nucleus are frequent, and enumerates as the only parts in whiub it dis- 
appears, the blood'Corpuacles, Che cells of the epidermis and nails, and most of 
the fat cells, the tubules of the lens and enamel, the bone-, and some of the car- 
tilage-corpuscles, and the gland-lu holes. But in all fibres that arefonned,as 
he believes, from fused or coalesced cells [with the exceptions of those af the 
lens and enamel), the nuclei remain and undergo remarkable changes, 
ciiilly, they are often elongated into tbin narrow corpuscles, reseoibling ^ 
dark stria, which lie upon the exterior of the cell-fibres (that it, tlw fibM 
which are formed fay the metamorphoses of culls, or whicli stand in the rdatv) 
of cells to the nuclei), in straight, ansiular, tortuous, or spiral lin 
being thus changed they may be nearly absorbed ; but more often thejr L 
furtlier developed, and send out filaments by wliich they connect ihemtelH 
into continuous fibres called nueleui-Jibres. i 

Henle describes two principal types according to which in these cases lij 
nuclciis-fihres are arranged. When the cell-fibres are cylindriform, as thoiea^ 
the fib ro- cellular tissue, they have the nuclei on their borders j when they are 
flattened, as the organic muscular fibres, the nuclei lie on their flat surfaces. ' 
In the former case the nuclei may lie in a row on one side only, and as 
they elongate and are united, they form a band along one border of the fibre ; 
or they may lie in rows altematelv on two opposite sides, and each may grow 
towards that on the opposite sioe which is at the next level above it, so at 
to form, when all have met, a spiral coil around the cell-fibre. In the latter 
case, that is, when the nuclei lie on the surface of a flattened cell-fibre, they 
have a tendency to send off lateral branches, and thus to connect theniselret 
into a net-work over the surface of each layer of the fibres. 

The formation of the flattened fibres just spoken of is peculiar, and seems to 
be an example of a class of changes in development, which were nut mentioned 
by Schwann ; those namely, which are efiected through the medium of a layer 
or sheet of structureless membrane. In the development of the coaU of blood- 
vessels, for example, layer after layer of cytoblastema in the form of struc- 
tureleHS membrane, is deposited ; and in each of these layers, nuclei are formed, 
which become tlie seats of several difierent changes. Cells may form in tbe 
ordinary manner upon them, as in the development of the epithelium of blood- 
vessels ; or they may remain with little alteration, as in the inner membrane of 
blood-vessels; or, at in the formation of nucleus-fibres already described, they 
may elongate ami arrange theojselvcs in rows. In the last case, which occur« 
in the organic muscular fibres as well as in those of the contraclilu arterial 
coat, each row uf nudei appropriates, as it were, the adjacent strip of the 



hoiDOgeDGOUS membraTie, which thuH breaks up into fliit fibrw, ench bearing thc 
run of nuclei after which it waa inoddted on its side or Hurluce. Lastly, these 
rows of nuclei may, in either of the two wbjb already described, elongate, send 
out filaments, and coalesce into straight, Bpirai, or reticular nucleus-fibres 
upon the surface of the flat fibrei. 

The structureless meoibrane may be produced at once R9 a kind of cytoblas- 
terna; but in certain cases it seeuis to result from the coalescence of a layer uf 
cells, as ia that which is called the feneEtrated arterial coat, and in the sheath 
of the roots of the hair, as well as, according to Reichcrt, in the layers of the 
cortical substance of the hair. In these cases also, another peculiar metamor- 
phosis of the membrane is shown. Cells in a single layer baring first united by 
their margins, and tbrmed a membrane, this, when thenuclei have been absorbed, 
and the cells are completely fused, becomes simple and homogeneous. Such a 
membrane ia usually stiff and brittle. Granules may now be deposited on it, 
and arrange themselves in rows, so as to form filaments which liave a longitu- 
dinal direction, or compose a. network, and lastly, the membrane is gradually 
•absorbed in the spaces between the filaments, and they alone remain forming a 
syntemuf fibres. Or, without such depoiiils of granules, definite portions of the 
membrane are absorbed, and a perforated or fenestrated membrane remains ; 
or, the absorption goes on so far as to leave behind only flat fibres in fasciculi, 
or in a network. 

With the aid of this sketch of the development of the elementary forms of the 
animal tissues, the plan here followed will be plain, and the few words said of 
the development of each tissue will probably be sufficiently int:;lliglble. 

From what has been said, it is plain that the process of nutrition is something 
very different from that commonly described as the result of the action of the 
blood-vesKels. Tissues are not laid down as such, but each forms itself out of 
a similar structureless material, and none attains its perfect form without pass- 
ing through several of the stages of development just described, over which 
blood-vessels seem to have no other influence than that uf being, in certain cases, 
the conveyers of material. In the embryo, before blood exltU or has been sent 
to any part, each part receives or consists of a similar material, which, by a 
power implanted in it according to a plan specially ordained for each creature, 
works itself into the peculiar form of each part. And when once a tissue is 
fully developed, the act of its nutrition is still the same. Each tissue abstracts 
from the blood, or otherwise receives, a similar material in the quantity ne- 
cessary for its repair or growth, and this material, as in the embryonic state, 
developes itself. Only now its tendency to assume this or that form ia in- 
fluenced by the tissue adjacent to it; for, with its perfect development, each 
tissue seems to acquire a peculiar power of assimilation, that if, of determining 
another adjacent substance capable of development to assume the same form 
iiud composition which itself has. 

In the degeneration uf tissues also, or in that which may be called their in- 
volution, as the contrary of their evolution or development, and which is pre- 
paratory to their removal from the body, they cannot be considered as lakeaup, 
or abaurhed, without change, by ubeorbent or other vessels. They probably 
retrograde through part of the stages through which they passed in their 
develupment, return to their former structureless or Biild stiite, and then mix 
with the fluid which is passing into the circulation for excretion, or for the 
nutriment of other parts. 

I. BLOOD-C0RPUSCl,EB, 

The discovery of the hlood-corpuscles by Malpighi' was one of the first fruits 
uf microscopic study, and since that event few objects have been more Eulici- 



ton sly ei 

cells, contniDing(»t lenst d 

nuclei, and harmg incorporiited in theui nil the red coluiiring matter of the 

a. Form and she. They nre circular in man and in all mammalia, except the 
Cflmel tribe in which they are elliptical ;' and the; are elliptical in all other ver- 
tebrata, except certain cycIoBlomeB in which they are circular.' In all, they are 
flattened and liave ruundsd borders. Whether their surfaces be ilightty concare 
or convex depends on variatiims in the quantity of their contents which may- 
ensue either within, orafter their remuval from, the body. In invertebrnta they 
are less numerous but more varied in form ; for llie most part they are irregular, 
granular, roundUh, nucleated corpuscles.' 

It is difficult to discern any strict connexion between the various sizes of 
these bodies and the other parte of tlie organism of different animals. Among 
raauimalia those of the elephant are the largest ;' then come those of the capy~ 
bara and rhinoceros i° then those of man, which have an average diameter of 
about g^ or ^^ of an ineh.° In general those of ruminants are smaller than 
those of other uiamuialia; and the smallest yet known are those of the little 
chevrotain and Napu musk-deer, of which the average diameter is less than j^^ 
of an inch.' An examination of the elaborate tables by Mr. OuUirer shows that 
the sue of the corpuscles in mammalia is not unconditionally propurtioniite to 
the size of each animal, or according to the nature of its food. Yet there is evi- 
dence enough that in each ^reat division of the class, the size of the blood-cor- 
puscles is, with few exceptions, directly proportionate to that of the animal's 
body ; and that, in general, those of omnivora are larger than those of carni- 
vora, and those of the latter larger than those of herbivora; so that ii the kind 
of food and the size of the mammal be known, the eize of its blood-corpuacles 
may he probably estimated. 

In birds there is a greater uniformity of size and shape in the blood-corpuscles 
than in mammalia, and, according to Mr. Gulliver, a nearer relation between 
their size and that of the body. They are the smallest of the elliptical hluod- 
corpuscles, those of the camel tribe excepted ; they are generally rather less 
than twice as long as they are broad, measuring about ^ by ^ of an inch, 
and about six times as long as they are thick. In reptiles, the largest and, hy 



Jaslice of the award ^Iven in fhe lent bf conaalting A. Kircher, (Scrntinium Fhya. Med. 
Feitis, Lip8.l659, p. 240 and the context) -, MBlpi)(hl, (De Omenlo, Pinguedine, dn:, |>. 42;) 
and hia Aatoblogrnphy in (he Opera PosthDms, (|ip, is, 92, in the FoL Ei. ;) and Svfbdi- 
Dieniam, (History orinsecta, Ant published in 1969, at p. 31, of Hill'a edition of 1178.) 
Lisln of the principal wrltflrs od (he blood -co rpuecles may be collected from the General 
Analomiea of E. H. Weber, Gerber, and Henle. 

' This remarkable and unexplained exception was discovered by Mnndl in thp drome- 
dary and alpacbu (Comptes Rendus des Sesncea de I'Acnd. des Sc, Dec. 30, ia3fl), and 
has been amply confirmed. 

= R. Wagner, (I*hrbuch der Physiologie, B.i. IS3.) 

' Wagner, Lebrbuch, and Beltn^ zur vergleicb. Phytlalogie. But be regards them 
ss only cbyle-corpaacli^s. 

* Mandl, (Anntomie Microsc. p. IT.} Owen (Conlcibutlona to the Conip. Anal, of 
Blood-dlsGB, Lond. Med. Gszells, Nor. IS, 1S30) saya moat of them am i larger than 
human blood-corpuscles. AccoiiIlDg to Gulliver (Appendix to Gerber's General Ana- 
tomy, p. 42,) the uveruge diameter is ^^ of an incb, which i« tieiirly nccordunl with 



' Oulllver, i. c. Ml I. 

* Perbapa the strictest 

In tbeae the nvenige i 



,*.•;: 



1 stated in/raclioHi of an Englieh in 
ania are those of Mr. Bawvrbank for 
I l>eing ,A, and ^. Coploi 
r^n K., t:l.(U, ■ ■'■■ 



lUn, (Allki 



B by dllTerenl oJutetveTa are given l>y Kiitllln, (Mlkroakop. Fotuchungea, , 
p. 55;) in the Microscopic Journal, vol. i.and in Mundl, I.e. (). 10, 
' 0*en,;.f. Dec. 30, l^^aBi and Gulliver. /. c. |i. 44. 



conpariaon, the thinneit, blood-corpuBcles yet known occur; and Wngner' 
marks it as a general rule, wliich Mr. Owen confirma, that the longer the br 
chilli apparatus persiata, the larger are the blood- corpuaclea. Thus, in 
ProteuB they are about jtj of an inch lung, in the Syren ^ hy ij,'; in i 
batracliian reptiles generally, about tabu by ^i^; and their thickneas is i 
more than one eighth of their length,' This rule, however, fails trhen c 
cornea to fish, in which the branchial apparatus is persistentand perfect ; for 
them the blood'CorpuBcles, though resembling those of reptiles, are genera 
smaller and less elongated.* 

b, Siriicture and Composition. The blood -corpuaclea are generally regard 
as primary nucleated cella, and no one doubts that those of birds and the low 
vertebrata coneist of an external cell, formed of an extremely delicate, soft, ai 
elastic membrane, in and within which all the colouring matter aeema to 
contained, and of an internal parietal nucleus, generally similar in form to tl 
cell, but about one fourth its size, colourless, and in the large corpuscles < 
some of theampbibiacontaining a number of distinct granules.^ 

It is queationed, however, especially hy Valentin, Wagner," and Gulliver 
whether the corpusdea of mammalia have nuclei, or whether the central spotl 
not merely produced by the accumulation of the colouring matter at the cii 
cumference. Henle> would decide the question by saying that, in a few of thes 
small corpuscles, there are nuclei; hut that in the majority (and these the mot 
fully developed,) there are none ; ao that he thinks it probable that here, as il 
some other casea, the nucleus, after the cell is perfected, is gradually ab 
Borbcd. 

According to Dr. Barry,' the young blood-corpuacle in all the vertebrata is i 
mere diac, with a depression in the centre. In mammalia it retains this furm 
in the other classea the diac becomes a nucleated cell. The nucleus at first com> 
municates by apellucid orifice (" nucleolus") with the exterior of the corpuscle, 
thia orifice occupying the placeof thedepressionin the original disc. The oriliac 
becomes narrower, and the nucleus finely granular, and these changes immediatelj 
precede the division of the nucleus into minute discs. Tlie discs, whose number U 
multiplied by successive divisions and by the gradual appropriation of the nui 
cleus from its circumference towards its centre, arrange themselves so as to. 
form a flat filament, having an appearance the same as that which he finds to bfl 
presented by fibre in all the filamentous structures ofthe body. According ta] 
the number of discs, this filament forma within the blood-corpuscle either a rinej 
(as in man and most mammalia, where they are comparatively few), or a cou< 
(as in birds, amphibia, and fiahes, where the discs are much mure numerous, and! 
the filaments proportionally lunger.) '\ 



' Lehrbuch, p. 133. ' Gulliver, in Appendix lo Gerlier, p. 

^ In the cryptobrancbuHjiipon[cua(in which there is no perulslentbranchlslopparatus}] 

ey meaiuroXby ,h (Van der Hueven, Tijdacbrift fur Naturl. GeacbiedeDJa, 1841, p,U 

0,)biitconBideringthegreBtBl; ''''" ""' ' ■■-- - .. . . - 

iuro|Kiilii>u ' 

' The ana 



bloud-coriiascles ar 



u thia reapect. 



ismeagur^J 



irrhicus lupus present! an enceptioi 
t^')}' j'flo' (Van der Hoeven, /■ r., p. 21i.) 

' In the blood- corpuscles of tile Siren, as many as SO or 30 granules can be seen In 
plane ol' the nucleaa. (Owen, In the art, Siren, Penny Cyclo)).) Tba proiwrflon 
longest carposcles ore thtne of the crocottilua luclus; they mBBKuTB about gjg by gijgg ol 
4in incb. (Mandl, C□m|)t(^4 Rendua. Duo. 33, U39.) Thuse of the Croc. ncuEua ham UN 
uauul elliptical form, their longer dlemeler being about twice as greut us the shorter.l 
Gulliver, Lancet, Supt. 10, 1842. 

* Lebrbucb der Phya., i. 154. '' L.c. Appendix, 13, undPbll. Mag., Aug. ISlitfl 

' Allgemeine Anatomtu, p.43j. 

■ PblliHiopblcal TransBctIon><, 1%4I, &c. The descrljition in the tent hii* boen k , 
farnldbHl by Dr. Barry bimarir. Comjian^ for confinnaljun, Mayer, Ueber Primlllvfnaem '1 
la Blule, (Fronep's N. Nolizen, April, iS4I.) ■* 



The filnneDt thui furiued is flat and deeplj grooved on both tarracN, b«a|r 
thereby thinner in the middk than »t the edges. Tht a\ges are rounded ; and 
wLen teeo on its edge, tlie filameot nt firat sight satmi ti> consist of sesmrnU 
separated froni one another by oblique lines. When perrecled, the filanient 
undergoes various changes : sotnetiiues unwinding itself into a straight fibre; 
at others, eontiouing circular, while smaller coils of similar filaments are formed 
within it from a residual portion of the nucleus. In all cases the filament is 
reproduced by self-diviaion, so that out of a single filament a fasiculus may be 
formed. Such changes are seen going on in coagulating blood. The filaments 
now mentioned exactly resemble those which are found in a great many both 
nnimnl and vegetable tisBuee, nor can any definite line of disrinction be drawn 
among the gradations from them to the double spiral filament, of which Or. 
Barry believes that the primitive fibrils of muscle, and certain other tissues. 

In nil cases in which a nucleus is present, it differs in cliemical characters 
from the cell. The colouring matter, orhsematosine, is easily soluble in water, 
by which it mav be completely washed out of the enveloping cells. The latter 
are composed of a peculiar albuminous substance (glol/ulin of Berzelius), which 
only slowly dissolves in water; tbe nuclei cunsiet of a different albuminous 
substance, more like coagulated fibrine, which is quite insoluble in water, and 
the^ contain so large a quantity of inorganic matter, that they completely retain 
their form, and, apparently, tbeir substance after combustion.' 

PurpoK. Or. Barry's and others' facts make it nearly certain that the blood- 
curpusclcB take an important part in nntrition, if not in providing the materials 
of the tissues ready formed, yet in giving them their due capacity for develop- 
ment. In some casesof reparation, indeed, as of fritctured bones, theHunterian 
opinion that the effused blood becomes the bond of union is strengthened by 
the knowledge of the changes which the blood-corpuscles may undergo ; but 
the present evidence is insufficient to make it probable that they.oraDy fornied 
parts of them, are effused in ordinary nutrition. Wagner and Henle suppose 
that during all their circulation, the blood-corpuscles, by the energy whiuh they 
like other primary cells may possess, are occupied in giving to the blood the 
constitution necessary for nutrition, secretion, &c. And this seems highly 
probable. It is nut so reasonable, fur example, tosuppuse that the effects of re- 
spiration are finished in the lungs, as to believe that tbeintluenceof the osygen 
dissolved in the blood, is accomplished during the general circulation, through 
the medium of these cells with which it is continually in contact, and which 
might tic compared to floating glaud-cells. _ 



II. LYMPH AND CHYLE CORPUSCLES. ^M 

In the villi of the small intestines, the chyle is a pure milk-white albuminous 
fluid, which does not spontaneously coaguUte ; its opacity is due to a number 
of minute oil-globules, varying according to the nature of the food, which float 
in it without any mixture of fibrine, or of the peculiar corpuscles which after- 
wards appear. Soine of these particles of oil, disllnguishcd by their immei 
ably minute size, and by a more general similarity of character than the othent 
present, are described by Mr. Gulliver' as forming the niukcular box of the cby^ 

' See Harting, (Gisaingea belrBffemleiieeorstevormingdercellan.ifec., Tljdschrlft ti 
uuturl.geBcbleilenlsen iibyilologie, 18-11,8 Deel;) anea^ay pointing out several re 
libli> nrinlogiei between the Imma atsomed by certnjn inoi^nic preclpi Isles (Huch at 
uf ttiB carbonnles a! lime aiul Iron) and the forma of the nuclei and cvlla of orgfln 
auei. Scenlao Link, (Puggendutf'a Annalen, Bd. 40). The best microscoplco-obi 
nualyala uf the blood -CDr|iu<cles is in Wngner, (Lehrbuch, p. 100.) 
• In Gorber, Apiwiidli, p. SB. See hIso his contributions, &c. Pbiiosoiihical Magg- 






iHH. 



Ucgidci thesti coiiBtitucnte, the more unlurc cliyle, eapeviiilly iirter it hns pae 
througli Incteal cknilH, contaius the proper ekyle-corputcles,* or cclla, which 
colourleEs, nioderiilety tranaparent, roundish hodiea, Boine larger, eome smal 
than blDod-corpuBcles, apparently composed of numernua granuleti arraa^ 
round one or more central moleouleB, These are probably produced by I 
development of a cell around a nucleus formed by an aggregation of a nil 
ber of the minute oil-globules which coaetitute the molecidar basis f and, 
the corpuBclea appear and incrRase, the oil-globules ditniuisb, and the chy 
acqiiiring a greater proportion of fibrin, becomes more firmly coagulable. 

The lympn-corpusclea closely resemble those of the mure perfect kind in t 
chvle. Some of them are generally digeemible in the blood, moving, as it ci 
culatee in the capillaries, in the peripheral portion of the current. They ai 
somewhat larger than the blood-corpuscles, (into which it is most probab 
that Ihey are ultimately developed,) white, strongly refracting light, roundi* 
and granular, or mulberry-like.' Their probable mode of development by tt 
aggregation of granules lias been already mentioned. 



■ jiEiE iiii: sooiii iuaiiLii,.dB of cells coDlainin°; oil at certain periods of tliei 
development, but those fo which the name of fit-cells is peculiarly gi^en, an 
the minute vesicles which, lying in the areola of the fibro-cellnlar tissue, coir 
stitutc the adipose tiRsue. These are true primary cells, whose contents art 
oil instead of the albuminous fluid with whieb most are filled.' They are, foi 
the roost part, nearly spherical, and vary from ^tOnm of an inch in diameter^ 
their membranes are structureless, and though remarkably thin, are, by Ai 
water which they contain in their pores, impermeable by the oil within theni^ 
and they are usually aggregated in bunchea traversed and enveloped by fibriH 
cellular tissue, conveying small blood-vessels." Sometimes each cell bears on it*! 
wall a nucleus;' and in their early periods the oil in each ia not in a single dropji 
but is composed of one comparatively large and several small drops, which sub-j 
sequently coalesce.' 1 

Afactmay be mentioned hereby which Ascherson' has endeavoured to explain 
the development, not of the fiit-cclls alone, but of nil primary celU; natnelv, thatj 
if a minute drop of oil be placed in contact with a solution of^albumen, it direetljri 
becomes coated with a film of the latter, so na to resemble a fat-cell. Any oni!! 
may observe the fact in preparations in which a greasy bone is put in weak'} 
spirit: for wherever the oil oozes slowly, the hone becomes covered with thiB I 
artificial fat, fur which the filmy envelopes are furnished by the albumen diseoWedi 

' Dlicovered by Leeaweiihoeck, und Orst well deccribi'd by Huwson- 

^ Tbey do not Indeed act aim ihitly on the npplicntlun ofcbtDiica] teals ; but the obaerva- 
tions of AscbereoD, presently to be mentioned, stiow Low it is poaslbte tbat in tbeir aggre- 
gation the miDutc molecnles may have (heir apparent chemical properties modilied. 

' The folleat hijtory of the chyle and lymph Is in Nnate, (Unters. Knr PhyaiologlH and 
Pathidogie, bd. ii. i and In Gerber (Appendix by Gulliver). See also Carpenter's Priqciples 
of Homan Pbysiology, p. 460. 

' Malpighl (Da Omento, ibc.) first described the adipose tissue with some nccoracy.. 
Fanluna (Traill surluVuninde la VlpSre, Ac) flrat clearly described its elemantajy cells: 
loRoiipail (Nour. Synt, de Cbimie oi^ntiique) and Schwann (Mlkroskopiacbe Untersnch- 
ung«n)t however, are due nearly all Ifau more important lacts regarding; their minute 



' See E. II. Weber (HildBbrnndt'»Anatomie,bd. i.),aiid KrausefAnatomiectesMem- 
chen, bd. 1.) 

* The«e are ailmlrabty ligiired by Maseagni (Prudrotno della grande Analamia). 
' Schwann (Mikrosk. Unlersuth., fcc. p. H4) ; Brans, (AllgBmeine Analoniie, p. 3i.)ij 

• Schwano, (/. f.) Henle, (Atl^. Anat., p. 181.} 
' UebtT den Physiol. Nutieo der FeltstoBB, JWuIlet'i Arcliiv, IS-Ill. 




in the water of ttie diluted Hicohni, It is nnt probnble that the liiGt Bdmtti 4 

»n exteneiTe application in the physiology of cell-derelopment i yet there J 
sufficient annlog; betiveen these artificinl products nad such bodies tu I 
corpuscles of the chjie, the eniniilated oil globules {cnrpi granuleux) of the m 
and some others, to render it probable that Iheir developmental process is ii 
great measure the same.' 



The physidlogy of cuticle hns received an nltogetber uew aspect from recent:! 
in vest! Ration s, nod especiiilly from those of Henle." He has shown that, with.' .| 
very few exceptions, all the free surfncea of the body, both those of the li 
ments, of the serous cacilies, of the mucous tracts, of the blood-vessels, and J 
of the gland-ducts, are invested by a membrane composed of one or more layers J 
of primary cells, forming a cuticle or epithelium. 

Forms and arrangeineiits. The elements of theM cuticles, however, have n 
all the same form ; and while they alt serve the common purpose of protecting' i 
the tissues beneath them, many, perhaps alt, add special functions to which they) 
are adapted by a peculiar form or energy of their elements. They are all, itt i] 
their complete state, formed of nucleated cells, in which, while the cell* in 
different parts present many varieties, the nuclei are generally round or oval, 
flat and colourless, or reddish f and the latter contain one or two distinct small 
nucleoli, and others very pale and small, and varying in number. The nuclei 
measure from nU to 3^ of an inch in diameter,* and the nucleoli about ^ as 
much. The cells are usually clear and colourless, but are sometimes beset with 
minute points. 

According to the form of the cells, Hen1e' distinguiahea three varieties of 
epithelium; but they are not separated by strict differences, for whenever a 
continuous surface bears at different parts two different epithelia, there ia k 
verv gradual transition from one to the other. 1 

The first is the Uaehited or pavement-epithtUam., which is composed of one or V 
more layers of flat, oval, roundish, or polygonal cells, each about ^ of an inch, \ 
in diameter, and containing a nucleus of the same shape, which a^in contains 
one or more distinct, and several paler, granules. This ia by far the most 
common form of cuticle: it covers the skin, and lines the ducts of the cutaneous 
glands, the mouth, conjunctiva bulhi, pharynx, oisophagus, numerous gland- 
ducts, the vagina and cervix uteri, the entrance of the female urethra, thesflrous 
and synovial membranes, blood and lymph vessels, and a few other parts; and, 

' The minute anatomy of the secernent glanJs might firiil Iti place her8,HincB It is 
probahle the real agents of secretion are iaolaWd primary calls ; but most of Ihe glanJa 
ate 0/ so complex aalructure, that It will be desirable to deacribe fltataome more oflheir 
component parta. 

I BBtani Ibeae inveati gallons the eiiistence of the grcHler part o( tbe intarnnl cuticles 
was argued rather than proved. Leeawenboeck (Select Works, bf Iloole, vol. ii. p. 126,) 
Ural dBBcribedwllh aome accuracy the acales of tbe epidermlaandof thsepitheliom of the 
mouth and vaginn. Delta Torre and Fonlana (Traill «ur le Venln, Ac, t. i. f. S-IO.) 
more clearly described the cella aud their nuclei in the mncua of tbe eel ; tben Rnspall, 
Breachet, and others gave account* of similar calls in the opldennia ; and then the cuti- 
claa of msnj different parts were descrllied by Parkinje, Valentin, and otherGerman ana- 
tomiats. The extslence (not the structure) of the opithellom of the intealines was shown 
by Liebetkubn (De fabrics et actlone Vitlorom). There la a complete tilsbiry uf tbe 
obaervBllons in this partof slructnralanBtomy In Honle, (Allgem. Anal., p. 259.) 

• 'i'hiB colour exista particularly in the nuclei of the youngest and deejioat layers, 
(Hante.) Dr. Barry {(. c,> points it out ba one nmong many analogies between the epilhe- 
ItDm-cells and tbe blood- corpusclea. 

' Henle, Allg, Anat., p. 2ii. 

> Ueberdle Ausbreitung des Epitbellumi, MUller'a Arcblv, 1838; and Atlgenieliu 
Anatomie, p. SiO, front which nearly nil Ibix accaant of cntlclei ia derived. 



mh general rale, hiuKtbicluieBS directly proportioned to the frictioD and otlH 
sources of injury to which it iaeKpoBed, 

Cylinder-epiChetivm, the aecond Tsriety, U found from the cnrdin, nlong th 
remninder of the digestiTe canal, to the anuB, in moat of the gland-duclg tha 
open on the inlerioruf this tract, and in the greater part of the male genito 
urinary apparatuB and the gland-duote connected with it. It i« composed o 



closely-aet celU of a somewhat conical, pyramidal, or cylindrical form, abou' 
-jXg of an inch long, whose apices are attached to the raucous roembr '" 

flat epithelinm-celU lying on it, and whose bases, which are usually U 



by a truncated plane about gibg of sn inch broad, are free. Each such cell 
encloses, nearly mid-diatunce between its base and apex, a flat nucleus witA 

In the ciliaiy tpilhelium, which constitutes the third variety, cells like thoit 
in the second have serernl fine, pellucid, blunt ciliK, about i^ of an inch lon^ 
attached to their free extremities. These, by means of some unknown ^oweis 
are during life in constant motion, either whirling their free estremities, s» 
that their ends describe circles, or waving continually backwards and fori* 
wards, and alternately rising and falling. Examples of this kind are found 
on every part of the respiratory mucous tract above and behind an imaginary 
plane drawn from the base of the naaal hones to the anterior maxillary spine^ 
even into the air-cells, in the lachrymal sac and canals, along the Eustachian i 
tube, and on the membrana tympani, on the palpebral conjunctiva, the cerebral \ 
ventricles, the commencements of the capsules covering the Malpigbian bodies,'-^ 
and in the female genital organs, from the middle of the cavity of the nterot i, 
through the Fallopian tubes, and for a short distance on the peritoneal surface H 
of the latter. | 

The modes in which the elements of these several cuticles are connected are ] 
equally various. In the tesselated epithelium the component celts, when there H 
are several layers, generally lie confusedly one over the other; and thuHe in eacb ' 
layer adhere by their edges with the smallest possible quantity of interccllulaF 
substance, their mutual pressure usually making each cell polrgonal. In the 
cylinder variety, the cells are generally almost in contact at their fixed extremU' 
ties, while their free portions are immersed in a soft intercellular suhstancei 
which fills all the spaces between them, and forms a smooth surface over them. 

Modes of devdapment and growth. What has been said of the structure of! 
cuticles, plainly indicates the change that must be admitted in tbeir phyaiolo^; 
Tliey are, in the most proper sense of the term, organized; for, besides tU' 
peculiar definite form of their elements, each cell has in itself the power bj* 
which it is developed, and depends on the subjacent vascular tissue only, u- 
all other elementary structurei do, for the supply of the materials which it maj' 
use for its own nntrition. These materials before they attain their ultimate 
form, undergo several changes, which have been best traced in the laminated- 
varieties of the tesielatedepithelium, including the epidermis and the thicke 
of the epithelia of the mucous membranes. In all these, the youngest layei. 
that is, those which lie next the vascular membrane or matrix, seem to consii 
merely of reddish nuclei, and these formed by an aggregation of granules ; th_ 
cells, if there be any, being too small to be discerned from the nuclei whicfci, 
they contain. As these are moved from the matnx by the new matcrialti 
successively deposited beneath them, both the nucleus and the cell, which l*i 
soon obviously developed upon it, grow larger; but the cell outstrips thfti 
nucleus, and at length assumes the usual appearance of an oval, nucleated* 
corpuscle. As they become older nntl still more distant from the matrix, th^j 
nucleus either remains stationary or grows gradually more obscure, while thtf! 
cell still increases In size, but becomes flat, dry, polyhedral, or quite irregiilarj 
and at the last (as one sees daily in the outermost layers of the epidermis) falli 

a, niso, (he exifilence I 



16 

off alone or united with many of its fellows in a shapeless scale.' In the nme 
prop^ress also its chemical constitution is altered : at first the cell dissolvei 
easily in acetic acid ; at last it assumes the peculiar characters of horn, and it 
altogether insoluhle in that fluid J 

In the cylinder epithelium the mode of growth is the same as far as the fortD- 
ation of the cell around the nucleus ; hut afterwards, instead of retaining nearir 
the same shape, the cell enlarges more in one direction than in the other ; and ii 
the ciliary variety it proceeds to the production of vibratory cilise from one of I 
its extremities. | 

Purposes, The uses of cuticles are probably, as already mentioned, variom. 
One is to protect subjacent parts, another to render certain snr&ces smooth. I 
But many may have more active offices. It will be seen that the elements (^ I 
the most energetic secretory organs have only the same structure as these hsTe; 
and it is not improbable, for many reasons, that the epithelium -cells also pn*! 
pare and carry off with them, when they desquamate, some peculiar fluid. Hk 
ciliary cells probably serve to fam onward the fluids and the minute particles in 
contact with them. The direction in which they act is most commonly, bot 
not constantly, towards the external orifice of the canal on which they are 
placed ; but in truth their special purpose is in many instances (e. g. the ceir* 
bral ventricles) as uncertain as the power by which they act.* 

V. PIGMENT-CELLS. 

In certain parts there are special organs for the production of colour, 
namely, in the pigmentum nigrum and uvea of the eye, in the memhnae of 
the ampullse in the internal ear,^ in the whole of the epidermis of (le lug^ro 
and other coloured races, and in that of the scrotum, the areolae of Cbb^masts, 
the labia and some other parts of light-complexioned persons.^ In moii olte^ 
the pigment is composed of minute, dark granules, collected in primary ei^)&. 
The latter, when they lie loosely, as they do on the iris, are oval or round; 
but when, as in the pigment of the choroid, where they are most distiBct, 
they are set closely and in an even layer, their mutual pressure makes them 
almost r^ularly hexagonal. They are nearly flat, about ^ of an inch in dia- 
meter, and lie m apposition so as to form a beautifully tesselated membrane. 
Sometimes their edges are in contact, sometimes slightly separated hy a pale 
line. Near the middle of each there is a clear spot, produced hy the nuclens 
of the cell, in which there are usually one or two nucleoli ; and around this the 
pigment-granules are arranged. They are most numerous in its immediate 
neighbourhood, are less thickly collected at a little distance from it, and at the 
very margin of the cell there are often none at all. They are collected also only 
at the posterior surface of the cells on the choroid ; the anterior portion of each 
cell (that is, that part which is turned towards the cornea,) contains the nu- 
cleus, and is quite transparent.^ In the negro's epidermis, perfect pigment-cells, 
like those of the choroid, are found only in the deepest layers, and are most 

' It hardly need be pointed out that these facts prove the distinction of a rete Malpigfail 
from the epidermis to be artificial. 

^ See, on all that relates to them, Sharpey, (Cyclopaedia of Anatomy, art. CtHa ;} 
Porkinje and Valentin, (Mailer's Archiv, 1835, and Br. and For. Med. Rev., vol.L 
p. 509) ; Pappenheim, (ilnd. 1840, p. 510.) 

3 Wharton Jones, (Cyclopsedia of Anatomy, Organ of Hearing,) to whom also is dot 
the first accurate description of the pigm. nigrum ; See Edinb. M. and S. J. xl. p. 77. 

^ Simon, (Ueber die Structar der Warzen, &c. Mailer's Aichiv, 1840, p. 151.) The 
black matter of the lungs and bronchial glands has no special apparatus. That whk:h 
tinges expectoration seems deposited in ordinary mucus-corpuscles, (Martin Barry, PhU. 
Trans., 1841, p. 226, PI. xx., f. 72.) The dark colour of many superficial nievi, of lifer 
spots, and of freckles, is due to cells of pigment like those described in the text, 
(Simon, /.c.) 

^ Henle, AUgem. Anatomie, p. 281 and 158. 



17 

lottoma of the fosaie between the paplllsi. 

from thOHc nlreftJy describeil, except in being amnller and in funning sever 
layers ; they sometimea Beem to hnve separate graaules, not inclosed in cell 
nixed with them ; nnd similar granules held together by the tenacious substnni 
" "ch they lie are found in the uvea. 
. pigment-granulea are among the minutest structures in the hndy. The 
tt, oval curpuscles, measuring about ^^ of an inch in their longest dia 
, and about J as much in thickness: so that, according to the dircctiun it 

they are seen, they appear flat or linear or like mere points.' When w 

free by the bursting of the cell, they exhibit a very active milecular motion: 
and Schwann has noticed the same occurrence even while they are inclosed. H 
is only when aggregated that they give their full dark colour; when isolate^ 
they are nearly pellucid, or their borders only appear dark, < 



Bruns' alone has accurately described the structure of the nail in the. 
adult. U consists of primary celli, almost esactly similar to those of the epi- 
dermis, firmly fixed together in several layers. The youngest cells (thoRSi 
which lie at theroot and in the deepest layers of the body of the nail,) are peU 
lucid, round, clongateil, or polygonal, nnd contain a round, granulated nucleus, ! 
with some other granular substance. They measure about ijjgofan inch in their 
greatest diameter, and their nuclei are about ^ as large. The oUleet and most 
BuperRcial cells are larger and broader, but much thinner and more irregular ia 
their shape. Their nuclei are rarely discernible; between the old and new 
cells, (hose which are intermediate in situation are so in structure also. The 
Striee and fibres, described by Gurit,' are due, Bruns says, to the section of the 
cetl-meinbranes ; the granules of Tourtual* are traces of the nuclei. j 

The growth of the nail is effected by the constant generation of cells at iti 
root and at its un Jer-surface ; and this process is carried on with the energy { 
necessary to repair the constant waste, both at the free extremity and the ex- \ 
posed surface. As the successive layers are pushed forward and toward the snr. | 
face, each cell becomes larger, drier, and flatter, and more firmly filed to those 
around it. The identity of tlie structure of the young cells of nail aud of ept> 
dermis, renders the question, whether the epidermis be continued under thq 
nail, one of words only; their early development is (he same. 



Vn. CARTILAGE, 

True Cartilage, The proper substance of true cartilage is a homogeneous 
and nearly transparent white basis, in which there are numerous small, 
round, oval, or flat and elongated, or sometimes angular, cavities (ciirtilagt 

1 Hi^nle, /. ii.p.284. 

' Lehrbuch, p, IST, Bafere examinHtion he makes the nail very son by immersing 
it [n an alkaline ley. His description exactly confirms whet Schwann bad proved of <ti 
dufBlopment. 

> Ualfn. liber die homigen Gebllde, (Miiller'K Archiv, 1H3T.) 

* HomsIoCrim Kropfen, (Miiller'a Arcblr, 1840, p. 2S1.) 

" According to their minute straclure the pnrtd commonly celled cartiEngea and fihro* 
cnrttlBgea may be thus divided (Henle):— I. True Curtilages ; tlie Btticulac (with soma 
excepllona presently mentioned), the costal, eniiform, nosaJ, trochlea, and (bose of the 
whole respiratory tract (w)lh a fe* exceptions). 3, Fibrous Cartliages : tile inlerverlo- 
bral ll^nments, the lyniJiondrasBs, the cnrtllaf^ps of the ear, epiglatti«, end Eustachian 
lube, tbo Suntorlnian and WtiaberKiun, Iba s tern o- clavicular interurliculor discs, and the 
cartilages of (he Inferior maxillary urtlcnlsUon. 3. Ligamentous discs: the interarticulu 
ligamanls of Ihe lower jaw, wrist, nnd knee-jolnbi (except the shariiedgea of the latter,) 
Ihu tnnal cattjldges, Ibe glenoid and cotyloid llgamenti*, and the flbra-carilliiges of tba 
ahealbi and pulieya lor tendons. 



eorpiacbi), from ^ to gjng of an inch in dinroeter.' The; utDRlly BMm to 
be mere cnvilics hollowed out in the bnsis-siibatance : but, by long boiling 
tbelntteris nearly disBolved, while they reuiain as disthict corpiiBcleB; and 
sometimes a liniog membrane i« discernible in them.' They are, therefore, 
to be regarded as genuine cells, whose vralla, during their derelopnient, have 
amalgaraated with the intercellular substance.' Each such cell encloses one or 
more round nuclei which contain nucleoli, and sometimes are surrounded by 
cells, BO ng to give those first mentioned the character of parenl-cetla, that is, of 
cells enclosing a second generation of cells. The secondary contained cells 
vary in number, and hure usually the form which mutual pressure gives them 
ai they enlarge. I'he nuclei are often filled by fine particles of oil, which are 
at fint iaolated, but may coalesce, and, when very numerous, may fill their cn- 
vi ties BO as to make them look like fiit-cellB; and when this takes place, the 
cavity of the primary cell also usually contains particles of oil. Bui in all 
these reepects, as well as in the character of the contents, of the primary cell, 
whether they be cells or nuclei, and in the mode in which the contained corpus- 
cles are separated or attached to the parent-cell, tlie varieties are manifold and 
as yet unexplained. 

The number of the cartilage-corpuscles, and the direction in which they are 
arranged, are more regular. In the articular cartilages, they Tire moat nume- 
rous and Rmallest in the part most distant from the bone. All of them have 
their long axes vertical to the surfaee of the bone, except a thin layer of those 
next the joint, which are flattened, and lie parallel to the articular surface. 
Hence it is that such a cartilage will crack vertically to near its free surface, 
and then tears transversely. In all other cartilages, also, most of 
puscles are set vertically to the surfaces, but there is a superficial layer ftf 
which they are flattened and lie parallel to them. In the cartilages of '*~'~ 
ribs, the internal corpuscles are arranged in rows which radiate from the a 

The substance in which the corpuBclea are imbcd(led is usually homogem 
and structureleBs, but in certain cartilages it gradually assunies a finely fibrous 
aspect, and ultimately becomes truly fibrous.* With these changes two others 
coincide ; namely, the formation of fat in the nuclei of the cells, and the acquire- 
ment of the yellowish colour in the place of the pearly blue of young cartilage ; 
and all these apjiear to be preparatory to ossification, 'for they are never seen in 
cartilages in which that change does not take place.' 

Fibroia Cartiloge$. The fibrous structure of some of the cartilajjes just 
described makes the transition to the fibrous cartilages, properly so called. In 
these there are corpuscles similar to those in the preceding variety, (espept 
that the nuclei most commonly contain oil,) but the fibres are much darker and 
coarser, and form the greater part of the tissue. In different examples the 
directions of the fibres vary : in some, as the symphysis pubis and interverte- 
brol ligaments, they are parallel ; in others, a« the cartilages of the ear and 
epiglottis, they frequently bend, and seem as if they were matted together. 

Between these fibrous cartilages and the ligamentous discs which are usually 
called flbro 'Cartilages, there arc also intermediate structures ; the fibres of 
the flbrouB cartilages are not tike those of tendinous tissue: thoBe of the liga- 
mentouB discs are. But in some examples of the former (the alerno-clavieular 
and inferior maxillary interarticular ligaments, for instance,) the chief sub- 



■ Meckaoer, (De penltiori cartllnglnnin atrnctur!l, Bieslnu, 1B3S.) 
in dlffBreat Bpecimens, see BrDi]i<, I. c, \\. 216. 

* Brung, Allg. Anot, p. 315. 
=■ See Schwann, (MlkroHk. Unlen^DCb, &c. ;) Heule, (Allgem. Annt., p. 104. ) 

* These flhres ail? not cleniuii-ilrs(»l by enapiiini; u cartilni^r usanUpr: [he fibrous 
liesrance of the broken gurfnoei', nnd the lilreclloo of Uib grain, nre Jnu lu llie urrnng^ J 
inent □[ the cart[]ugc corpuscliui. 

» Heole, AUaem. Anal., ii. tV*. 



neot^^l 




19 

til trftversedbjiagciculiDf the fibrilg of cellular tissne, andtliuB tbe trM^ 
sition is eHtabliahed from them tu the ligaiiientouB diacB, which iire coinpoi 
GDlirely of that tissue. 

Devehpment. In the enrlieat state yet seen, cartilnge roaBistt) of its uorpuaclM 
set very closely in n soft homogeneous cytoblftetema, nnd containing ;t clear 
fluid And nn oval nucleue on which they ivere probably developed. As the cor- 
puscles increase in size, so does the intercellular substniice in quantity and density; 
and gradually the walls of the former are amnlgamated with the latter, so thM 
they deserve the name which Henle has given them of cartilage cavities, rather 
than that of cells. With this coal esc in^t, the cavities of the corpuscles sometimes 
become smaller as if by a lamellar deposit on the interior of their walls. New 
cells areat the same time produced within the older ones, or in the intercellular 
tubstance, or in both at onee. In the first case two or three cells form within 
one parent-eel) ; in the second, new nuclei are generated, and on these cells 
form as in the first development. To this condition the development of all 
cartilages is similar ; the prepress to the several varieties, is or will be described. 
Tlie growth of cartilage (distinct from its development,) is effected by the ad- 
i^tion of cytobtastema to the surface of that which already exists, in a manner 
similar to that of the growth of bone. 



Bone is composed of a basis of apparently homogeneous substance' (a compound 
of cartilage Snd earthy matter,) in «hich are densely scattered minute cavitie* 
with delicate branched canals. Thecavities (or bone-corpuscles,') are round or 
oval, and flattened ; tbey measure from about ,^ to ^ of an inch in lengthy' 
from lis l* iJm '" breadth,^ and are about \ as thick as they are long.' '1 hej* 
have somewhat jagged edges,'from all parts of which there proceed fine branch"- 
ing canul^ (calcigeroue canals'), which tritverse the basis substance, and com- 
municflle irregularly with ohe another. The diameter of each canal, at its ' 
largest part, is between nim s"'' mim °^ ^^ 'Dch ; that of the smaller branches 
is between nin, and jjfcj." Miiller' and Menle' have held that the corpuscles 
aud canals arc the chief seats of the bone-earth ; but Mr. Smee° has rendered it 
more probable tlmt they contain no solid matter, by showing that they can be 
filled with Canada balsam, and that, in the boufs of those who have been em- 
balmed, they are full of a waxen material ; and Bruns'° has found them empty 
in calcined bones, and perfectly transparent in very thin sections. At most, 
therefore, the e<vrthy matter is only more thickly deposited in the walls of the 
corpuscles and canals than it is elsewhere. J 

True bone always presents these elementary structures, and is thus clearly distia-J 

' An eiceplion will jirt'sunUy be menliuned in which it ii«eme to he fibroiu. Dr.^ 
Carpenter (Prineiploaot Human PbyBiolosJ, p. fill,) thinks (hat It id entirely composed 
ofcetU adherent together, nnd fllled with a perfectly homugeneoas tvbxtaaoe. 

' Tbey ware obicurely aaun by Ltwuwenhoetk (Select Workp, vol. ii. p. ISBj, and 
bsdiy figured by Mancngnl, (Prodromo, Tav. k., xix.) They were Ural clearly discerned 
hy Piuklnje, and diwcrlhtti by his pupil Dautscli <De penitiori atruclurft DBBiam. disa. 
inaug., Breslau, IS34.) They have since bean chiefly illnstraled by Miilier, Ml 
Schwann, Heule, Smee, nnd Brnns. 

_' MlBschor, (Dh Inflnnininllone Oasium, p, 42.) The measufBinenla of Valentluj 
KrauBK, Brans, nnd others are aufficiantly cunflrmatory. 

' Henle, Allg. Ann!., p. 82S. 

^ These also were dlscoversd by Purkinje, nnd more clearly described by Miilier. 

' The latter from Miillar, In Mleaoher, p. 36B ; the former from Kraune. Hoth ai 
confirmed. 

' In Miescher, p.8«8. " Allg. Anal,, p. S2B. 

" On the Structure of normiil and adKenlilimm Bonn, {Mfl-i. CmMh; Nov. 20. 

" Allgem. Anat., p. 241, 



guuheil from man; morbid subHttinces which are cnlled osBificstioni, but which 
coDBist of amurpliouB or cryaUlline depogitB of earthy mutter. Ue coarser 
■tructiire is variously nrraDged in different pnrts, but always pregRrvea a gene- 
ral characUr uf laraells! arranged round tubes and cetlular spacea. The com- 
pact structure consists of DBseouB lamina from i^ to g,^ of an inch thick,' 
firmly united in concentric tubes, or in parallel planes, accordingly aa the 
bone is cylindrical or flat.' They are moat distinct on the exterior of bones, 
for there they are rarely interrupted by the canals for blood -reSBcU, which 
more internally are interposed in great numbers between them, and send off 
branches which pass through them. They appear either homogeneous or pel- 
lucid, or a little granular, (like ground glass,] or sometimes very finely fibrous, 
like the fibrous portion of the second class of cartilages ;' and this last appear- 
ance is met with especinlly in cartilages ossified late in life, as those of the 
larynx, ribs, &c. 

The blood-vesBels of the compact structure of bone are conveyed in long 
cylindrical canals, (Haversian camils,") of which the chief run straight in the 
spaces between the lainince. These give off small branches which pass ob- 
liquely through one or more laminse,* and form communications between the 
longer canals in different planes, so as to make up a coarse network of bony 
tubes permeating the compact Etructure; they open externally to admit vessels 
from the periosteum, and internally they merge by a kind of gradual expan- 
sion into the cells uf the cancellous tissue. They are usually cylindrical, and 
they vary in diameter from ^ to g^ of an inch,' tliose nearest the surface being 
three or four times smaller than those near the cancellous tissue. Their walls, 
which are from jjj to ^ of an inch thick, are formed by from five to fifteen 
concentric lamelle' of bone : and thus, each Haversian canal, whether its 
course be longitudinal or transverse, is surrounded, as the whole shaft of each 
cylindrical bune is, by a series of tubes, arranged concentrically about its axis. 
The bone corpuscles lie thickly scattered and as if compressed between the 
lameltie, and are so placed that one of their largest surfaces is turned from, 
the other towards, the axis of the canal. The calcigerous canals run both 
between and til rough the several lam ell » ; and, since many of them are di- 
rected towards the axis of the Haversian canal, they look like a set of f»int 
Btrite radiating from it to the outermost lamelljB. Their apertures are ilis. 
cernible in amiill dots on each lamella, and, according to Krauze' and Mr. Smee,' 
on the interior uf the Haversian canals, intu which they believe that soiue of 
them open. 

■ MUller, Deulach, &c. 

' The mIcro9CO|)e wua hiirdi; needed for thus deciding ILe question whether boaea 
arc [oimed of lumeltie. The evidence of old GngUtirdi was coNcluaive. Certnindisenaes 
xepariite Iheae cuurwr lamells ; and after sotlenliig jii acid aome may be dis^tecled from 



composed of Hlamenls; but tbene were artiflcially-mBdo fibres, ultogelber dlHerent from 
le which are diacernible but not BepiirBble. 
' From Clapton Haven, who described tliem verj' fnncifuliy in his Osteologin Nova, 



In nse. 

' They form the little processes which GaRllnrdi (Anatomi 
nn nails. 'I'he accorncy of his account of tbe struetu™ of boi 
different from tbe ridicole communly altacbei] la bis name : tl 
Havers, wblcb is usually praised, Is Jiot nearly so good. 

> Mlescber, *c. ,|, to 4,. Bowerbank, in Medical GbmII* 
are best eeen In sections of the Dal bonea of the Anti, mat 

' They are called Inmellip for distinction from the laminir, j 

> Haitdbucb deri^iiatomii' di>' Menfcben, b. I., |t. 71. 
« Mnllcai Gazelle, i. c. 



Ossium, 188B) described 
B mBrils Hometblng very 
desciiption of C'luptoa 



21 

Eacb HHversian cnnal contains an artery and a vein, which pais along its axis 
surrounded by a very 8oft fat, to which tbey diBtribiiWniinutebmncheB. The ves- 
sels of the external canaU are derived from the perioBleuu j thoseof tbeinternkl 
ones froiri the vessels of the medullary tieaue; and the two seta freely anastomoso. 

As already s^ud, the canals of the cumpuct tissue gradually merge into tlu 
cellsof the cancellous; and in both the type of structure is the same; fur eacb 
cell also contains soft fat in which (he minute branches of the medullary artery 
ramify, and the walls of each are formed by a series of delicate lamellv, wttni 
corpuBclcs and canals arranged in the manner already described. ' 

Development. All bones are developed through tlie medium of cartilage: even- 
in those which seem to be produced in membranes, the cartilaginuus state in-' 
tervenes between the membranous and osseous. The development of cartilu^' 
to the state ready for ossiRcatiun is described. Tbe cartilage rurpuacles becunis' 
the bone-corpuscles, but the exact nature of the changes which they undergo is 
not certain. (See page 7.) Whatever it be, the deposition of earthy matter dues . 
not commence till Uie canals from the corpuscles and those fur the blood* >. 
vessels are formed, and the latter have received their supply of blood. 

The Haversian canals are believed to be formed by the parent cartilage-cellv i 
or cartilage cavities elongating and coalescing in connected longitudinal an(|L 
transverse series. At tbe parts which are not about to ossify the cells liefl 
aluiust singly; but where that change is at band, numerous young cells ars'i 
aggregated within parent'Cells in lines which have the same directions as the>, 
subae(|uently- formed vascular canals. The youngest cells then dissolve, and the 
caoal formed by the coalesced parent-cells becomes filled by a transparent semi-, 
fluid gelatinous substance (the cartilage-inedalla of Miescher), into which tbs 
newly-fonned blood-vessels enter from the periosteum, and in which they give 
off branches as afterwards they do in the Haversian canals. 1'he cancelloWi 
tissue is developed on the same plan; but the canals formed are much sborter* ! 
and their communications more numerous. The laminated and lamellat«d3 
structure is not disceuiible till after the formation of (be canals, but it seems toj-i 
precede tbe deposition of tbe earthy matter. The latter begins in the inter- 
cellubir substance and the vascular canals, in which minute dark granules am 
deposited evenly or in heaps ; the corpuscles and calcigeruus canals afterwards 
have their walls densely ossified and the process is completed. 

IX. TEETH. 

In no organs have the results of recent microscopic researches' been so un- 
expected or su brilliant as in these. They have revealed structures before 
unknown in each of the three component parts of the tooth.' 

Ctmcnt, cruita pelroia, or ione, foruis tbe outermost layer of the teeth, and in 
its minute structure difl'ers in no respect from common osseous tissue.' It visiblj 

' Tbe chief dlacoverisH were made coiaoidently by Purbinje, al Breslnu, and Retxiiu, 
oFStockbulm. Thu former published bis oliaeriBtloila la l>t3a, In the disseitoliona of 
Prtnkel (Do penitiori dentlum hum. Bliuclutft), and of Hiuchliow (Meietemata circa 
dvntiam evolutionemjj tbe latter in the Trunanclions of the Royal Academy al' Stock- 
holm, Bod afterwards In MUller'a Arcblv, 1N31. SeeBr. & For. Med. Rev. vlil.]58. Inter- 
esting as wera the facts tbey rBVealeJ. they nte far surpassed in importance by the 
application which Mr. Uwen, in his admirable Odonlogtupby, has made of the minuts 
structuroaf the teelb as evideuee In dalorminlngthe genaiatandgpeclfic rtlstioua of ei- 
tant and fossil animals. Itmuiil b«regr«tled that more nse canaot bemodeof bid 
in 80 limited a report as this. 

"Mulplgbl (Aoat. Plantarum Idea, p. 19, and Op, postbuma, p. S3,) seems fli 
iiave daBCTibwl ell the three BUbstoaces. He calls the bone materia tnrlarea, tbe ei 
tabilaatia fitameKtuta,iaii tbe dentine or Irory laitliiiilia ottea. Tbe bone wa4 s 
(|uenUy overlooked (ill tbe time of Purkinje nnd Ketxiua. 

' lis structure hIwbj's coincided with thai peculiar to tbe bona of each bj 
(Owen, (. c. XX.) 





{HMcil of « Sl>rutu baut WA i m wi Vf *tiir !■■, k>MlB^ crfiaMtd liAa 

wlikh run in an unMMtaf NHM lirttm the Ml^-cavkv. aa ar'kMB iaHnivM 
u)>ea, towMnh lk« M^tnot fsn «f ih« cxterwr «f tke'ttwtk. &A MMHfl 
iUcounu uulw&nk mifcMtw*orlkti 
in, bmiiit^ bent M tmrr f«n i*lu bm. _ _ 
(wvuikfory iiir*a/itr«i, Cnren ;> but llw «t 
i:«[it to eiMh iilher U tu ncarlr u puwtUi 

the (ubut«a are dieholumous; but ihcvali* fica^aaBllTgiie aff ■ 
which, ag*ia Mailiag off smatler oom, Ut ap the ip—M Wtwa^tfec iNMfcn, 
At the trunk each tubule has an -i-rnxT ih^tyr rfilinal i^ wf ■■ nmh, amt 
the iliataace between each twu tuboka is •boBl «qital to ite vUth of three. 
Ttiwnnls the outer surface of the iratj, the tubolaaad tkir hoailwi are i^ 
luenguntbly fine, and sunte of ihein pu* from the Way into Ibr booe, umI oycm 
into the canah of its corpnacks. Both the walk aail cacilks af tfcc uhirin, as 
well as the substance between Ibem, are filkd b* the earth; eoaMiiacBt of the 
ivory which lies in Gne granules. The basis o^ the interliibiitar tabataBoe Is 
composed, according to Heole,' of bundles of Bat, pale, granular Ghie^ whtMe 
f uurse is parallel to that uf the tubules. 

Development. Accordtog to Sir. Goodsir,' who bai admirably illustraleil the 
— :~:..Q tirst diitinct]]' announced b^ Arnold, the first appearance of tba pulp 
h > — 11, ;. ;_ .K» f 1 .g pspilU, riuog from the bottom ot k 



of each tooth is in the fonn of a n 



' Threa Mem»)r* on the Tivtb ami E|iitbe1iiirD ; nnd M«I.-Chjr. Trans., n>L exH. 
* A* in llDnlcl'a HiMrlinent* ii( firafling the loolb in tbr. cack'i comb, and oF ban*- 
planllnit leelb from ons nsruon loimitber. Oweo; Odunlogropb^. 

■ 8('liw(ii.ri, Dr.hiir ili^ V.-hjiMtnlImmina, *r,, p. US. 

' Mii'i' j'p'ilnd Bn hiring imllced the tobuUr or ftbroui siructore of 

Ibii/'" ■ 'rimlnn Ihn fi\iir.ei eituBily referred to will find Ihal ha 

nUK'i iify 'llMcimi^ u teniae flbrun* network like Ibat of which 



• /,. ■■, |i. •>/.». Mr, \n-mylJi emfUliil/ It In ■>• CBllidiir, {Memoirs-) 
<(ln Umilttittii ami J)m«ln|iiiH«ntiir llw nil|M and Itiwi ot Uiu Humun Teelh. EJiob. 
' 111 Mliil Nil'K' Juilrlii, r. Si, )!■ Ifil), 



Next, as the borders of the groove grow around it, the papilla Bi-enia to eiiik in 
the mucoiia membraDe, and appears as if rising from the base of a follicle^ 
Laetly, proceexea of nienibrane or o/iercula grow from the eides of the mouth of 



the follicle, and convert it into a capsule or aac. These three stages of the forms*' 
tive organs, the papUlaiy, the Jblliiular, and the copsu/ur, being complete^; 
the substances of tlie tooth begin to be fornied; namely, the dentine in Ihft, 
papilla, which assumes the form of the tooth-pulp ; the enamel in a tissue of 
enamel-pulp developed from that part of the Kac which is opposite to the papillaj 
and the Done in the sac itself, or in a tissue produced by it. 

The space between the papilla or pulp and the inEenor of the sac enlargin|r 
by the growth of the latter, there is deposited within it a soft, granular, non^ 
vaaculnr aubsCimce, tlie enamel organ.' At the same time there is formed on 
the surface of the papilla a peculiar structureless membrane — thepreformative i 
membrane' — which, when the pulp begins to ossify, presents numerous little i 
derations and depreBsiuns, in which the enamel-fibres are afterwardB Gxei] ; ' 
for aa the pulp enlarges the preformative membntne comes in contact with thi i 
enamel organ, and they are moulded the one on the other. I 

The tubules of the dentine and the prisms of the enamel are formed bytrans' I 
formation of the primary eells of which the pulp and the enamet-organ are re^ I 
apeclivcly composed. The superficial pulp-cells, which are at firat round and | 
nucleated, assume the same diameter and regular direction as the dentine tu- 
hules, and then have earthy matter deposited within and around them. And 
these changes go on gradually through the pulp from without inwards; as fast 
as the cells of one layer are ossified, those of the layer beneath elongate and 
arrange themselves regularly in preparation for the same change ; and so on^ 
until a great part of the pulp is ossified.* The pulp then begins to grow on^ 
wards into the jaw, forming one or more processes, by the similar ossificatioit' 
of which the fangs are formed ; and the tooth is thus made to rise to the eurfact 
of the gum. In the formation of the enamel the primary nucleated cells on tbc 
inner surface of the enamel-organ become elongated and cylindrical or polygo- 
nal; they assume a direction vertical to the surface of the pulp ; and their nucld. 
disappearing, they are hardened by the depositionof earthy matter within theni, 
and they coalesce into the complete prisms. These changes, like the preceding, 
make progress in layers, but fromjwithin outwards, till nothing is left but a thni 
ouiaiel membrane on the surface of the crown of the tooth. By the tranaforma, 
tlon of this or of the sac itself, (or, more probably, by the ossification of a nitb. 
terial effused from them as from a periosteum,) (he investing layer of bone or 
cement is fonncd. During the hardening of the pulp the preformative mcm- 
Lirane disappears or is ossified. 



Must of the hairs consist of two distinct substauces : an external, cortical, 
hard, and fibrous part, and an internal, medullary, granular portion, on which 
their colour chiefly depends.* Moderately mngnifit'il, hairs look like cmpt* 
tubes, but in fine transverse sections no central apertures can be seen. 

The cortical port of the hair is fibrous. Very delicate longitudinal strin mtif 

' Exlemnl pulji, of Hunter, (Natural tlistory of the Tevth). Organoii Adaniantini^ 
ol Purklrye, /, e. ^ 

' Fiist noticed by Mr. Bell, (Hunter's Work*, y. ii., p. 30, note.) 

' Hcnca the caucenttic tlngn of coloured dentine In young animals Ted on muJder. 
TliesuccAuiveij elongited c«1U must ulso be fueetl at their exlremllles, «i as tu lorn 
continuons lubt». It is nncertnln when the brancbea are giveu off, and how they com- 
iiiunicnle with the 1)otie-coT|iufcles. 

' Tba niediillu ii iiliwnt in the Una hulr over the geat^rul surfaci' of llii: body, mid tM 
ilie very rout Hiid nuur Ibe Ii|toIull hnlr 2 




be tnicetl on it, becoming more faint »s Ibey pass from the root to the ti 

ia genernl invUible at a little distnocc from the latter. Tliey t 
through the whole thicknese of the cortical eubstancc to the very v 
medullary portion, nnil indicate the outlines of the component 
latter are, according to Henle,' each nbuut njni of hd inch in brendth, flat, rieM, 
and brittle, with dark and rough edges. But they may probably be furu^ 
•plit, for, after maceration id hydrochloric acid. Bidder* found the diameter oi 
the thickcRt part of a eingle Shrc to be only ,^ of an ioch, and Brum* abovl 
10^ ; BO that prob:thly each of the fibres whose course is marked by tJie it 
is made up of several smaller ones. In some hairs, moreover, the fibres appev 
at certain parta, either irregularly or at dehnite distitnccs, enlarged ; and Hiiii 
the whole shaft sometimes assumes a beaded appearance.* 

Besides these longitudinal striai, indicating the fibrous structure of its cc 
cal part, the surface of the hair is marked by tramtversc and oblique, and m 
times apparently spiral, wavy lines arranged in a very close seriea. Meyer* bw 
shown that these are formed by the slightly projecting edges of tiers of minule 
scales, like those of the epidermis, hot much smaller, which, being closely in 
bricated in whorls one over the other, invest the whole surface of the hair.anl 
form a sheath around its cortical part, entending nearly to its tip. l^ymikr 
the hair look as if it were irregularl}^ Aao^ round; or rather, when the hair it 
very strong, as if it were a closely -join ted reed. 

The inferior tnedullary porlioit of the hair is darker than the esterior and gra- 
nular. It ia composed, for the most part, of very minute globules, lite pig- 
ment-granules, or drops of oil agglomerated in small luuip?, and enclosed in i 
membrane which lines the tube of cortical substance. Sometimes tlifffi^n- 
nules form one dark masa, continued along ihc whole shaft of the hair;tu(iuare 
commonly the mass seems broken up, so that there are intervals ol differesl 
sizes along the axis of the shaft. These are sometimes filled b3- astAnUnu 
like the cortical part, and the medullary matter then seems altogether deficient; 
but more often they are occupied bv a culourlesa substance, clearer anil suftn 
than the exterior fibrous tissue. 1 he diameter of this medullary part, nlieii it 
is completely formed, is about J or] of that of the whole shaft; transverse tM- 
tions of hairs exhibit it like a nucleus, with a clear ring around it ; along itt 
walls there are often complete pi gnt em-cells, with clear nuclei ititd transparent 
memhranes.^ 

At the tip the hair gradually becomes more and more fine, and iiEually eaili 
in a rounded point, at and near which neither sirisc norniedullary Gubstancecao 
in general be seen. At the root it rather suddenly enlarges into a funnel-shapEd 
extremity, which Henle has named the knvb of the hair, and which is atMiul 
three times as wide as the shaft. Just before the hair begins thus to enlarge, 
the trdDBverse striee produced by the outemioat layers of imbricated scales, sR 
very distinct and broad ; but they suddenly cease to he discernible. A t the muk 
part the longitudinal stris become finer, and seem to diverge. Uut, in additian 

' Ueber die Struclor ond Bildung der menecblicben Haaie, (Froriep's N. NothOt 
April, 1B40, and Allgem. Aoulomie.) 

* Binige Bemerk. iiber Enalebung, Bau, und Leiien der nientcfalichen Haact, 
(MuUer'B Archiv, 1840, p. £38.) 

' Allgem. Anatomie, p. 201. < Bidder, /. c. 

•Froritii'sNalizen, 1641, nnd In Henle, Allgem. Aiiat. p. S94. Henle coincide! in tik 
view: he tind formerly (Fror. Notlz., April, 1S40,) con^ldercil llie transverse strtie lotc 
due to bands oF a suh^tnnce resembling the elastic IIhsup wound round tbe bunLtUsi>f 
fibres farming thD shaft ; a view which closely agn^es wilb Ibut of Dr. Barry, who tl^ 
lleves that the bair has the same general structure as tbe muscular fibre, &c., and b 
composed of a fasciculus of Rat, double-spiral fibres, held together by wider coulocni 

■ ■ Vulpnlin (Kepertorium, Ifil,) und Relchert (Miill. Arch. IS41, clxxvi.) in- 



to these, the knub is marbtd by coarse, dark, longitudinal stria:, which look like 
short, interrupted furrows, but which arc produced by smnll, flat, metamorphosed 
nuclei, about ^^ of an inch long, and ^s, broad. They arc largest at Hie up- 
per part of the koob, nod are often tortuous or connected together by Bne Gla- 
nients ; lower down they are broader and oval or spindle-sliaped, and lower 
sliU they pass into roundish or angular granules, like the nuclei of the rete 
Malpighii. They lie closely in a firm, pellucid subHtaDce, and sometimes seem 
surrounded by cell -tnembranes, among which, in dark hairs, numerous pigment- 
granules are scattered.' 

The knob of the hair and the nearest part of the shaft are pretty closely in- 
vested with a membrane, for which Henle proposes tlie name of the ihcnth, and 
of which Eome or the whole is pulled out when a hair is plucked from the skin, 
it is continuous with the epidermis, and may be regarded as the epithelium 
lining the hair- follicle. It ii composed of two layers, of which the outer am) 
thicker is yellowish, granular, and thickly set with superficial nuclei ; ihe 
inner clear and much thinner, and perforated, like a,/imeifrafFiJmerniranc, by nume- 
rous round, oval, and elongated apertures, but having no trace of cells orlibrfs. 
Below, the two layers are united together, and with the exterior of the knob ; 
above, a small space filled with fatty matter intervenes between them and the ex- 
terior of that part of the shaft of the hair which is below the surface oftbe skin. 

Xr. CELLTILAR AND FIBROUS TISSUES, OR FIBRO-CELLCLAR TISSUE.' 
All the tiuues whiclt have passed under these names nearly agree in their 
microscopic structure : their chief anatomical diflerences depend on the mode in 
which their elements are aggregated. The common matenal of which Lhey are 
composed consists of fine, transparent, undulating, cylindrical filaments, from 
kAb lu 1^ of an inch in diameter.' They are generally collected in fasciculi, 
from g.^ to t^ of an inch wide, the filauienti in which are connected by a firm, 
structureless cytoblaatema ; and the fasciculi either merely adhere together, or, 
HE in the case of tendons and other similar tissues, dense bundles are united by 
others of more loosely connected filaments placed in tlieir interstices. In dif- 
ferent parts either dense or loose fasciculi, or both, are woven into cords, mem- 
branes, &c. 

in certain situations the elements of the tasciculi are bound together by small 
filaments of another kind, which, from their supposed origin, may be named 
luckus-JiUimenU, and which Henle' discovered by immersing fihro-ceflular tissue 
in acetic acid, so as to make its proper fiisciculi transparent. The latter are 
thus Been to he severally, and sometimes collectively, constricted at pretty re- 

' See also on this unbjecl some rematka bj Mr. Busk, in lheMicroacD|>ic Jonrnal, vol. i. 
|i. jfl, and vol. II. ; and Simon, Miiller's Arctaiv, IS'll, and Btil. &, For. Med. Hev. xiii. 
&iS : awl on the structure of the boir In geDeral, Reicbert, ^.c, 176 ; who believes that 
Ibe oorllcnl nubslance is compoaed of coneenlric layeru of rigid, pcUucid menibraiie, 
longitudinally Suured. On tbe develoi^meiit of balr aee Henle, Reicbert, Me3Hr, and 
Sidder, I.e.; among wtiom tbere is so mucli diSarence, that it tsimpoaeible to stale briefly 
vbal ii most probable. 

' This compound term aeema preferable to either of Its components. Fibmat and eel. 
lu/ar are both tertnii applicable to nluny tisanes besides Ibis ; butfitro-ecllular may well 
indicate a tissue composed of fibres which are in some caaes woven so as to inclose Im- 
perfect Eellnlnr s)Mce>i. 

' TreriranoB (BeilrKge, bd. i.), Jordan (Uebcr das Gewebe der Darlos, MUli. Arch. 
1S3J), Gerb(:r(AllB. Artat., p. 1J3), Henle (AUg. Anat., p. 3K), and man; others nearly 
agree In these measurements. Laulb (Nouv. Manuel de I'AnntomlstB, <fecO and Krauaa 
(Hoodb. der Anal., bd. i.), rnake them much greater. 

< The best tlaauo for demoiistrntlag tbis is that which forms the line fibres connecting 

e nerves and vessels at tbe base of tbe brain i but a similar arm ngeme lit eible iiinenrly 
every tariety. See on that in the pia mater of Ihe epiiiill tori) I'urkiiije and Lueuins 
(Volenlhi'a Re|«Tt, 1841.) " 



^ 




^^W' - 




■*p . _ 












J ;»^-r ■ I 



#■• . 



«* * • i**** 



r t 



^ ^n\ .^, 









' t - .k£ . ^ 



••<:i-*ii.".- 




* x^^ ■ ^ o^^ ^ .• "t^^r 












examplei of daatic tivna into three varieijea. The £nt, of wliieli th« type ifl 
in the true vocnl ligaments, differs only in degree from the interstitial fomi ^ 
the tissue which it combined with the fibruH:e11uhLr fasciculi, its fibres af^ 
undulated, narrow, and very rarely branched or anastomosing; they form, buw« 
aver, independint fasciculi, which are connected by small quantities of tha> 
Gbru-cellufar tissue. In the isecond variety, which includes the ligamenta tab^ 
flava, (the most perfect of all the exaraptes of the tissue,) the fibres are largs 
and widely arched, and frequently givu off branches. In the third, iucluding 
the elastic coat of the blood- vessels,' the fibres are of smaller size than in tht 
second, and very frequently anastomose so as to form, while they for the most 
part maintain one general direction, a network with maslies of various size,' 1 
When the elaalic fibres seem to branch it is doubtful whether a single fibra ' 
really splits, or a double fibre divides into its two component parts. Valentia,* | 
Lnulh, and Eulenherg maintain the latter view ; Schwann, Bruns,< Henle, anAn 
most others, the former; and they regard a genuine branching and coalescing 
as the peculiar characteristics of these fibres. In Dr. Barry's opinion the rett^ 
cular arrangement of some of the varieties of elastic tisauR, whose fibres havt 
the same general characters as those more simply arranged, afl'ords a striking 
example of the brenking up of double spiral fibres into networks, which would 
find a close analogy in the formation of the reticular ducts of vegetables. 

XIII. MUSCULAR TISSUE. 

The transition in function, though not in structure, from the passive to the 
active fibro-cellular tissue, and from the latter to the organic muscular tiasu^. 
has been already alluded tu. Among the tissues of the present class there are 
similar gradations in regard to their several functions i> but by their structure 
they may be definitely arranged in two main divisions: the first including the 
musclcsof organic Hie, which (with one exception] cousist of simple smootlt 
filaments; and the second comprising the muscles of animal life and of the heart, 
which consist of compound and apparently slriateil fihreij, or lubes, includine 
fibrils. 

■ To be mote MnulBly describe)! in another section. 

' The elaalje Iwoe occurs in dlatinct fasciculi in several parts besides these mentioned 
HS types of its rariaos arrangements. For instoDce, it Is found la the bauds and Ugatuenta 
o( the lorfni and respiralory po^aages, in a layer surronndiog the cesopbogns, ouJ la onft 
b»lween the muscnlni and mucous coata neur the cHniia and Ibe anus, ijj the fascia lata, 
and several other rascix, where, besidea the tnlerstillGl aud spiral DacleuG-fllamuoln,nuui]i 
independent faaclcnli exist. In Ibese parts the urraiigement is on the plan of tbe first 
varlely. Similar laiciculi, but usually arranged in nel-works, are found mixed in tbe 
lisue beneath the epithelium of several ^<e^□ns membranes, as Ibe pleura coatalis, lb« 
perlloneum on tbe anleriar wall or Ibe abdomen and on the fondua of tbe bladder, tho 
ligaments of the liver, the inleslines, &c. And, laady, fuacicull like those of tbe llgamunla 
■uhlliTa, are mixed with tbe proper tissue of many parts of tbe sltia. (See Eutenberg, 
Lanth, Henle, L e., and Bowman, CycL of Anat, art. Mucaua Membmae.} 
' IU!|iertorliim, bd. II. Elc. 
' AUg. AOBt. p. 75. 

* The BBVeral members of this ascending series may ba thus arranged ; — 1. Cooimoa 
connecting Abro-c«t1nlar tlssae. 2. 1'he tiaiDe of the skin contracting under the inBii« 
ence of cold aad mental emotiona. 3. Tbe dartoa, wbtch contracts more forcibly undw 
tbe some inHoeoces. 4. The contractile coats of arteries and veins. S. Tbe Iris, whicb 
conlrnctq wben Its nerves are directly IrrilatEit, and with the quickness of muscle. S. Tha 
lower organic masclea of tbe gland-ducts, &G.; and tbe higher of the stomach, urinary 
bladder, dec. T. The muscle of the heart, S. The pariecl mascles of animal life. But 
It will be observed that the progress hi stroctHie does not coincide with this arrangement 
acf otding tu forictlon. The llneuv of the Irin, for instooce, is exactly like the lowest 
nbro-cellular tidsiie. 



A. Miada^OTganK life. No full accouiit <>r this tiuue was gWea berore 
Uiat by Henle, wlio infestigaUd it in hU search after the properties of arteries.' 
Hkhvi that thefibrea, in their moat perfect form, are flat, from ^ to i^ of an 
inch brand, very clear, granular, and brittle, bo that when they break they 
often have abruptly rounded or square extremities. Some of them are unifonn ; 
a faw bear nnclei ; the majority are marked along the midille, or, more rarely, 
along one of the edges, either by a fine contiuuous dark streak, or bj short 
Ilulatcd dark lines, or by dark points arranged in a row or scattered ; and be- 
tween those three kinds of marks there are such gradations as orove that they 
have all the same origin from nuelei. Fibres sucli at Ibese are collected ia diver* 
numbers in fiiBciculi, upon which the dark lines just mentioned sometliuea form, 
by brnnclies which they give off and receive, a sort of network, and sometiraea 
run tortuously, like the nucleus fibres of the fibro-cellular tisaue. (Seepp. 8,26.) 

Fibres of organic muscle, such as are here described, form the proper contrac- 
tile coats of the digestive canal from the middle of the (esophagus' to the exter- 
nal sphincter nni,^ uf the urinary bladder, the trachea and bronchi, the ducta of 
glandH, the gnll bladder, the vesiculce seminales, the pregnant uterus,* the arteries 
an J the vein*,* 

B, MuKlti ^f anifoal life, 1'he voluntary muscles are composed of fieshy 
bundle* Inclosed in coverines of fibro-cellular tissue, by which each is at once 
eunneclod with, and isolated from, those adjacent to it. Each bundle is again 
divided Into smaller ones, similarly ensbeathed and similarly divisible; and so 
nn, through an uncertain numberof gradations, till, just beyond the reach of the 
unaided oyo, una arrives at the primitive faackuli, or the mmcutar fibres peculiarly 
so called, the first fixed form in the eyatem.' 

1. Structure. Theprimilive fasciculi consist of tubes of delicate strnelure/eM H 
membrane,' cncluslng a number of filaments. They are cylmdrifomi, or pris\^^| 
matlc,* with five or more sides, according to the manner in which they an cont^^f 

S missed by adjacent fasciculi. Their breadth varies in different animals, froot^H 
1 •" i4n "f »" 'I'ob i '"> iiiln from ^ to ifo, the average of the majority being* ^ 
about iJo'" Their most «lrikine, though not constant, characteristics arc their 
pale yellow colour, and their being apparently marked by striEs, which pass 

I (fahar die ContractiUtst der Geriaae, (Ca«|ier'a Wocbenscbrift, Mni 1840, und Brit 1 
* Par. M«d. Kit. vol. x.). and Allg. Anst. 

* On the FlltrM of the (Enopbagua, see the observation a □[ Mr. Gulliver, Proceed, of 
Ihn Sioolofflcnl Snvlaty, (lartvlil. 

* In til" flliri!! of the alomncli and intestines Uiere ia often an obscure division Into fine 
riKliI niiilllii ; III lljini' III tNt- ii|i|iflr [lart of Ibe uroters there is an approiimalion to the 
niito-i'i'lliiliii /.> ' II nil, Uir lliry gcniluBll}' ti|]lll lutu undulated hbrlts, (Heule.) 

* HiliwmM, (Mikii. ii rm.-r». II. laj), Liiutl) (Mail. Arch. 1 835, JalirBsb, p. 3), and 
Half , til MiiiN-i'.i i'ln-i.ili.Kj. Un those of Ihe unimpronnntoil nterns, which resemble 
Iti* UMit«vi'li>i""l iiiuniuliir libren of Ibe embryo, see Purkliiju and Kasper, Proriep's N 
Nollx. Mnrx IN'12. 

* tt«<ifnrlhHr, p. 3U. 

* Thtty wnrn lint described by Hooke, in l&1%. The account of tLem became ^adu- 
ally morn accurate In the successive descriptions of Leeuweuhoech, Muys, Funtana ntnj 
I'roeliixks. 

' Valentin (Her.ker's Annnlen, 1§351; Schwann (Mlkrosk. Unlera.) It is Ibe snrco- 
lunimaor Mr. Itowmnn (fhlloa. Trans. 1840), whose complete ileecrlplion of it ia gene- 
(Hllf cunllrnwil by Henle (Allg. Aiiat. p. 5lB). Tbe latter, bownver, adds tbat It isonen 
ahfant i and that, when [ireaeut. It bears nomerotis elongated nuclei like those on ttis 
IsmIcuII of ornnlc muscle. 

* Muyn (Mnsculoruni Artlllciosa Fabrics, pi, i.) ; Procbaidta (De Came MuacuUirt 
ji, ia)l Ilowmnii (_t,c. PI. ivl. % I, (fee.) 

* Howmnn (/. c, p. 4110). These measurements are generuUj' confiimed by those of 
Itaspoll, Schwann, Shey, Uenle, and others. 



29 I 

tranBTereely round them, in slightly eurfed or wavj pnrnllel lines, from ^^ ttf 
lAa of an inch' npart. Other, but generally more oliscure, Btricc also paM 
longitudinsll y over the tubes, and indicate the size and direction of the fllamcnts^ 
or primitiTe fibrillK of which the priraitire fiisciculuB is composed.' 

The priini(iwjI6W& are the proper contractile tissue of the muscle. Each of; 
them h cyliodriform, but sumeurhut flattened, and about ^^ of an inch in it* ' 
greatest thickness,* They are marked by Iransrerse impressions, which arc 
at exactly the same distance apart as the strite on the surface of the fascicuitlgl 
Hence it is generally coocluded that, as Fontana believed, the striated appeaiw i 
ance of the primitive fiisciculi is produced by the lilarnents being so apposed . 
that the transverse marks od all those near the surface lia at exactly the same 
levels.* At present there is much question of the true structure of the fibrils, 
and of (he souree of their seeming constrict ions, or transverse impressiotifc 
Some deny the existence of such constrictions, except when the muscle is con- 
tracted, or in some particular condition after death;' some believe that the 
fibrils are rows of corpuscles, or discs, connected by a homo^neous transparent 
substance f and Dr, Barry' regards the fibrils as a peculiar form of his grooved 
and compound filament i each being composed of two spiriil threads, wouod 
in opposite directions, and interlacing. In the second view, (he trans. 
verse marks on the fibrils, and the ordinary strls on the fasciculus, correspond 
to the spaces between the discs; in the last to the spaces betweei^each two suc- 
cessive turns of one of the spiral threads; for since each filament has its edge I 
turned outwards, only one set of coili can at first be seen. I 

Each primitive fasciculus contains several hundreds of the fibrils ; and when I 
fully forme<l they fill all the cavity of the sarcolemma with the exception of 1 
very small interspaces, which seem occupied by a glutinous pellucid fluid.' It 
is only in immature fasciculi that there is an appearance of acentral cavity, which 
is filled either by fluid or by minute granules.^ 

Where a muscle is ufflxed to a tendon, each primitive fasciculus of the former 
terminates in an abruptly rounded extremity, which is embraced by a fasciculus 
of tendinous fibrils, expanding and enclosing it as in a sheath.'" The coarser 
fasciculi of tendinous filaments are also continuous with the fibro-cellular tissue 
which intervenes between the secondary fasciculi of the muscle. 

2. Action. The actual phenomena of moscular contractioo have been often | 

' Schwann, in M iiller's Physiologie, bii. ii. p. 33. Nearly coafiimed by Prevoat and I 
Dumlis, Lnulh, Bowman, and others. T 

' Eicepllons Id tliese ^norsl characters are met with sometimes, but are not yet ex- 
|ilniiied. See eapeclally Gulliver in Uerber, p. W5, and Henle (Allg. Anut., p. 5Sri). 

' The tneaxuienienls oF Henle, Lsuth, Ficinua, Bruns, and several others, pretty 
nearly sgiee with this statenietit. 

' Ur. Barry, however, (Philosophical Transactions. 184S,) nays there are stales In 
which the ilbrills have no sbnie in the appearance of transverse slrlse, and In which they 
are ilae lu the Hat and grooved &hiTnents, which, be believes, are wound aplnilly and In- 
l4^rlBced oroond tbe bundles of Bbrllls. Some aS Henle's obsuvalions are strongly con- 
Rimatory of this view (Allg. Anal. p. S83) ; and perhaps Mandl's accomit (Aoat, .Ml- 
croac. p. H,) b drawn froui a similar ippearnnce. 

' Trevlranos, (BeitrSge, bd. Ii.;) Fioinns (De Ftbra muscularls forma el structura;) 
Valentin, (De Functionibus Nervuruni ;} Skey, (Phil. Trans. Wil.) 

* For examples (esch, however, with some modification,) Laulh, Krause, Tarpin, 
Schwann, MUlter, Bowman, Bruns, and Gerber. 

' L.e., and Phlta.''uphicBi Magazine, April, 1H4J. Henle, (Allgem. Anal. p. 5li3,) 
cunfe?Mi'S it Impoiilble to decide the quesllon, but he seema to think that the fibrils ore not 
composed of rows oF globulea, but derive that appearance from being finely wrinkled. 
Fonlana, nUo, (Sut le Venin de la V1p£re, t. ii. p. Sid,) remarked that the appetinuioD 
xeemed due sometime* lo rows of globules, and al others to the mere wrinkling of cylinders. 
' Skey, Bowman, llenla. ' Skey, Gerber, Henle; bat see Valentin, p. 31 . 

" Valentin. Bowman, Bruns, itc. 



cKaminei] in bntTi (he voluntHrj nnd the involiintftrj' muscles, bat the mode in 
wliicti it is eflpcted is still JispittcJ, Hnlet,' and nfter him Crevost and r>umas,' 
dcacrilted the roatraction as the result of the primitive faseicuU being thrown 
iiilo zig.iag lineB. But the view of others (which has beeo eapeciiillj' illustrated 
by Mr. Uuv/mtui'), is tliat the Ghange h effected by an approsimatioQ of the 
constituent parts of the fibrila (tvhether discs or coils), which, at the instant of 
contraction, without any nltention in their general direction, become closer, 
flatter, and vrider; n condition which is rendered evident by the approximatioo 
of the transverne strite seen on the turface of the fasciculus, and by its increased 
breadth and thickness. The appearance of lig-zag lines ia referred by Dr. Alien 
Thomson and Mr. Bowman, to the relaxation of a fibre which has been recently 
contracted and is not at once stretched again by some antagonist fibre, or whose 
extremities are kept close together by the contractions of other fibres. Valentin' 
adopts B middle course of explanation, believing that the production of inflex- 
ions in the fibres depends on the degree of their contraction. Ordinary and 
moderate muscular contraction, he says, is eCTected b^ a vermiculation passing 
very rapidly over the whole length of the fibre, and in this act, the transverse 
strioi are approximated ; but when the contraction is greater, geniculate (zig- 
zag) inflexions are produced, and become the more acute and close, the more 
violent the con tr>iction. AUagreeintheaccount of the contraction commencing 
either at the Atremity or at several intermediate parts of a faaciculuB,and thence 
travelling over its whole length ; so that the entire act is rather a Bucceswoo of 
contractions and dilatations than a single contraction.' 

In relation to the question of the connection between the muscular contnwti- 
lity and the nervous influence, the following observation by Valentin may be 
recorded, but perhaps shonld not lie built npon without much caution.' He 
galvanised on the field of the microscope several minute portions of muBde,and 
observed whether they contracted or not, which it was possible to do <cilh » 
moderately high power. Then, with a much higher, he examined whether, iu 
each portion of muscle, there were any portion of nervous fibre included ; and 
he fuimd that in every case in which nerve was present contraction took place, 
but that when the portion of muscle contained no nervous fibre, the galvanism 
was inefi'pctual to produce the same result. 

Deixlopntent. Schwann's account has been already alluded to. It is thai 
nuclei, with nne or two nucleoli, form on a sofi cytoblaslema, arrange themselves 
in rows, and produce cell -membranes around them. The cells thus formed 
become filled by granules, elongate, coalesce by their cKlremilies, and rorni long 
tubes, within which the fibrils are produced. The latter have at first the appear- 
ance of fine pellucid filaments, which are produced in layers from without in- 
wards, so as gradually to fili the cavity of the tube or secondary cell ; and ai 
they are formed, the granules that were in tbe cells disappear, and the nuclei tut 
pushed towards the wall. Valentin's' account differs somewhat. He thinks thai 

■ Statical Etaay», vol. ii. p. S9. 

' Mem. sui lea Pb^noni^nes qui BCcoini). . . ile to Fibre niimulslre. (Mng«ndiB'i 
Joaroal, vol. ill. p. 301.) 

> Phil. Trans. ISIO anil IMI. See abo Owen and Allen Thomson, in Huntet'i 
Works, by Palmer, vol. It. p. SUt. note; and Martin BsiT}, /. c. 

■ De PunctlonibuB Nermrom, p. }3i. His abdeTTatlons were chiefly made bj gain- 
nliio^ porliond of muscle on the field of tbe mtcmscope. 

■ On the npiilicalion of Uiis to ruptDres of muscles, see Mr. BowmHU's PapRr i'l 
the Pbll. Tiana. H4I. 

■ Aud the more Kince It has not been conBrmed, and Mr. Bowman aajs that in his ei- 
penmentf fibrils contracted after, as he believed, all adjacent tisauas were complfitcj; 
remDied. It la possible, however, that these were each apnriona cantractions aa, acconl- 
init to Valentin, are produced meielf by the action of water. 

V ZoT Entwickeling der Gewebe desMuskel-.des Rlnlgefass-, und des Ncrven-Syilcnu. 
MiiUer*! Aicbii, 1410. Meule (Allg. Anal, p. (MN» nvorif coincid(~i. 



31 

the fibrils inajbe produced nutaide the tubeformei] of the' coalesced CPllR,»nillh!ie 
UiU latter mnj' fiirm (nl least for a time) the wnll of a cr.Dtntl cavity whicli, lie 
believes, alvrnys exiHts in the inuaculaT ^ciculus. Tlie fibrils first produced 
are, he sajs, homogeneous nml pellucid r the; nftcnrards become raricose, and 
the muscle assumes its striated furui: and hence the two kinds of fibrils may 
often be found, the simple in the interior, the varicose in Ctie exterior, of tlje same 
fesciculus. He is aIbo disposed to regard the saroolemma as a secondary form- 
ation rather than as produced from the coalesced primary cells ; believing that, 
' the cvtoblastema remaiDing around each fasciculus of fibrils, Ducleatei) cells 
3 produced, vhich arrange themsehes longitnilinally, become luneand narrow, 
Mid at last, by their fusion, form a sheath of fine varicose fibres. The nuclei of 
these external cells are what Schwann supposed to he the original nuclei pushed 
outwards from the interior of the fasciculus; Valentin believes that the original 
nuclei are absorbed together with the granules which at first filled the cells and 
the tubes formed by their coalescing. 




A, Structure. 1. Ctrebi 
system one finds 



)-a>'in(il nerDoH! Jibret. In a nerve belonging to this 
fibres enclosed iu a common membranous sheath, or 
neurilemma. The latter is conjpoeed of fiaciculi of fibru-cetlular tissue, closely 
woven together in a generally longitudinal direction, and somewhat more wavy 
than the filaments in most varieties of this tissue; so that they give the nerve 
a satin-like glistening aspect. Commonly, also, it has a characteristic striated 



even spimt), from a 

to the fibres of the neuri. 

us fibres within it being 
re destroyed by stretching 

e assorted in subordinate 



appearance {the 8tri» being transverse or oblique, 
alternation of bright and dark streaks, which are di 
lemma being wrinkled,' or to the primitive nen 
nrmngcd in a slightly tortuous manner,' and which 
und by maceration. 

Within this common sheath the nervous fibres 
bundles of nearly equal size, each of which is enclosed in a separate secondary 
sheath, continued from the external one, but composed of much finer and less 
perfectly developed tissue. Within each of these there are again subordinate 
Oivisions of the fibres similarly enclosed, till at last, arriving at the primitive 
fibres, each of these is invested by a covering analogous to the outer neurilemma, 
but possessing a fineness of structure proportioned to the minuteness of that 
which it envelopes. It is a most delicate membrane, exactly pellucid, and, in 
eeneral, seems structureless ; but SchwauD* believes he has seen elongated nuclei 
'in it, nnd Valentin* says he can, in favorable circumstances, see that it has a 
fibrous appearance, " as, if two sets of fibres crossing one another ran screw-like 
round the nervous tube ; a view which remarkably confirms the observation of 
Pr. Martin Barry.^ A longitudinal arrangement of fibres is also sometimes 
discernible.' The proper substance of the nervous fibre, which is contained 

■ A better example of the progrcaa o( minute DDslom}- in four yeara cannot be found 
tiian In scomparl«on oMbe Tutlowing nccnuntwilb thntlnareclew, in BiiLife For. Med. 
Itev., voL vl., of what wns known on the BBme snhjecl in 183S. 

' PievDat nnd Dumas, Valentin (Ueber den Verlauf und die lutiten enden iler Nerven, 
Nov. Act. Acad. Nat. Cur. 1836, p. 88.) 

* Fontonn, («nr le Veuln, AcO Unrdacb, (Beitr. znr MIkroak. Anat. der Nerven, Ann, 
des Sc. Nat, I83T, p. 117;) Henle, (Allg. Anal. p. (116.) 

' MlkroBk. Unteraach. 

' In SSmmeiing (vom Bane dcs menseh. Kiirpers bd. v. )>. S.) 

^ Heule baa n less diallnct description of a similar urrDngoment ul inlerliiclng dpiml 
fibres around the primitive fibre (Allg. Anat. p. 020). 

' RoKentbal, Valentin. Vulontln (Reperloriiini, Hi. 20°) believes be bus somL'timef 
menls n» if produced by cllias on the Inner surface of this primniy shuatb ; but 
much conlidence in hin observutlon (Sommciliig's Anatomle. bd. v, p.H); and 



within the iTttath just daer'ihtd, if, ai;eon!iDf to ValcNUa,' s dear ipilitiil 



cln, or Rbm. Hcnlc, ^, ._ 

ncnoui fibre u resembling, in the lining or juit-dead rtate, a ■or ijliatrrf 
ctear flasa, being pelluci'l and colourless, and hariog UBiple, vc11-4cfiaHl,W 
edgea. Bui IhcT a^rer that it it onl; immediatrlT aAer renocKl t^MMiife 
pticily of composition can be d'ttceraei ; for vrry qcueU*, uaj c^ie ~ ~ 
they are imH.ereed Jn walir, the 6bre», as if by a coaenlatiM) of tfaeii 
auume the appearance of being composed of two diScrmt BiaSerials.* hC 
itate their edges are mariced by dark parallel outlines, vi^un sbi^ 
tiro ititemal line*, parallel (o thcni and to one aootber, wkich ■ 
fihre look like a tjbe. 

Regarding this latt at their natural condition, Reniak,* whotti 

agrees very nearly with that of Fonlana,* conaiJer* esch fibre a« a i 

tractile tube, contaioiag; a pale Battened hand (the prnaitrre ti^d) wVA,i 
thiDks, is composed of several very fine solid filaments. Rosenthal,* also v~ 
description was written under tlie guidance uf Purkinie, re^nlseacii &bre b 
homogeneous, but as composed of an aiit cylinder, of moderately Gm nv 
matter, enclosed in a cortical portion of softer substance (regiita ^^itMiriiy 
nearly the same view is entertained by Hannover' and by Schwann. Or. Mtil 
Barry, on the other hand, believes that the nervous fibre possesses a stn 
analogous to tUat of the primitive fesciculus of muscular fibrils; tkat iIk 
while substance (vugina meduliarU) is a fasciculus of double spiral flat filan.„.~, 
and the central portion {Ranak't band) a filamentous material from which they 
are continually being given off- 
Whatever he the true original structure of the nervous fibre, itt erliodriatl 
is soon exchanged for a beailed or varicose form, from the accuinabliuMoflhe 
contents into separate masses, which dilate small portions of the shcathiUActlhe 
intermediate spaces collapse; and these changes proceeding, the contenHof the 
sheaths, either spontaneously or by the influence of the fluid in which the; ait 
placed, assume a ^rauular or curdy appearance, and may be easily pressed int. 
From the supposition that these states are natural, arose the errors in the fini 
descriptions of minute nervous structure by Ehrenberg' and others. "IV 
changes take place with the more facility, the more coarsely the fibres alt 
dissected, and the finer and more delicate their investing sheaths are.* llMi 
are therefore quickly produced in all the fibres of young subjects, and in thoN 
uf the brain and spinal cord, and of the nerves of peculiar sensation at iD 
ages. Hence Ehrenberg was led in bis first essay to make a marked distinctiM 
between the varUoie filrra in these nerves, and the cyliodric fibres of othcni 

' In SiimiDerlag, p. 5. 

' Alls. AnaUSn. See also Klencke, Uber die Prim itivnerrenrasem, 

* A isct lemaikablj confinnator; of tbte view, and of vhicb tbe firal notics u dnetl 
Mr. Clid, 1* the perfect liaDiparencf of tbe living or jiut-dead retina; Itasaumes theinV 
o|«clty b) wbirh 11 ii generally known in Uk «me lime as tbe change here described ii 
■uppoied to take place in tbe nervous Sbres. Still, however, though Uie whole subdlam 
nuy, during life, jweni homogeneous, its Bepanition Into two difTorpnl materials when It 
li all ■ubjecled to Ibe lame Influence, makes it moat probable Ibut the external and JnW- 
nal portiun* ate tetilly illfTereiit in ttaeir cotnpiMKion. 

• Obi. AnaL el Micr. de Syatematis Nervos* Stmctori, Ftorieps N. Nulfzen, Jgsl 
IHM, and In Mveral other patwre. 

• Sur le Veiilii de ii VIpere, tec. 

* Dl-ii. Iruiug. de formaUanegranaloB& in nervis.d-c.in Valenlin'a Repertorium 1840, 
p. T8, file. ' 

' Hiiller's Archiv, l«10, p, 5M. 

■ Beubachl. alner aufhilUnden . . . Struktur Jes Seelenorgatii, Berlin, 1S3S. 

■ (Jn th> Intoence nf particular a^ntii in prodaclng these changes, see Buidacb 
VnlenUn.and Umie whoaJwglve* ' 



irove tFnt ur, 



ud although bis own later obserrationii, snd those of all othera, prove tl 
nervous fibres are bIIIcp, in their natunil Btatp, cyliodrical, yet, aB Keinuk hat 
observed, the dagrees of fiicility with wliicb they severally BBsunie the beaded . 
form uiny serve to dislinguiih tliem as well as if they posBesaed it during life, 
le size of the cerebro-spinal primitive nervous fibres is variable, and the 
fibres have not the same diameter through their whole length. They are 
nlly largest at their peripheral extreiaities and in their course along the 
trunks, where the majority measure, in round numbers, from ^ to . 
^,^ __ . inch in diameter.' They gnulually decreaie in siie as they approach J 
the brain, whether directly or through the medium of the spinal cord ; and in the | 
brain itself they continue to grow less as they pass through the medullary to the ' 
cortical part, so that in the former they meaBor&(on a similar general average) I 
from ^ to HBB "nd in the latter not more than i^ of an inch.' The fibres of 
tiie olfactory and optic, and, in a less degree, those of the auditory nerres, are 
equally Bmall in every part of their course, and thus resemble, insize as well as 
in sEructiire, those portions of the other nervous flhres which are continued into 
the nervous centres. Remak^ also observes that Che primitive fibres for common 
sensation are smaller, and become wore readily xaricose than those for motion ; 
and Henle* confirms this in general, but adds that there is no distinct line of 
demarcatioD between the two sets, for that in all mixed nerves fibres of every 
gradation of size occur. 

2. Orgenic or sympathelk nervovt fibres. The general neurilemma is tougher 
in this iTian in the preceding class of nerves, and has a layerof circular fibres in 
addition to the longitudinal ones. The several fibres in a nervous trunk are 
seldom assorted in secondary or more subordinate fasciculi.' 

In the nerves of this system there are, besides the fibres supposed to be pe- 
culiar tu them, many of the same kind as those already described ; and the 
latter, which are always finer than the average of the ordinary nervous fibres, 
vary in their proportionate number in difierent parts. In the roots of the sym< 
pathetic they do not form more than J or J of the fasciculus; in most of the 
nerves proceeding from the ganglia to the viscera they are more numerous ; in 
the main trunks, such as the splanchnic and the cardiac nerves, they greatly 
predominate; and the ciliary nerves, as well as those of the lachrymal and mam- 
mary glands, and those which accompany the blood-vessels, are wholly composed 
of fibres like those of the nerves of common sensation." 

The nature of the other and peculiar fibres in the branches of the sympathetic 
nerves has been much disputed. They are described by Remak,' Pappeiihein: 
Muller,' and some others as distinguished by their fineness, paleness andyellot 
ish hue, and by the constant absence of the lateral, dark lines which give the I 
cerebro-spinal nerves the aspect of tubes. Rosenthal and Purkinje'° consider J 
them to be formed by an axis-cylinder similar to that of an ordinary nerve-fibre, I 
and surrounded by a granular nucleated sheath ; so that thev differ from cerehro- J 
spinal nerve-fibres only in the absence of the outer medullary layer (vagina 
meduilarii,) of the nervous substance. Henle thinks they are a peculiar set ol 
nervous fibres arising from the central organs, put into connexion in the gan- 
glia, and destined for the contractile fibro-ccllular tissue and the blood-vessels. 

' Wagner enil Krnose, (Miiller'a Pbyalology, by Baly, 1.^91;) Noise, (Miiller'sArchiT.j 
IB3D,p, S4fi.} The muBiuremenlsorseverBl others agree. For comparison, see Ehrenben, / 
(/. e.) and Wngner, {In BurjBch's Phy»iologle, IkI, v.) * 

' Treviranus, (Beltrage, hfl. li.;) Henle, (Allg. AnaL) 
VarlaufigeMUtheKungen, (Miiller'a Arcbir, IB3fl, p. Ufi.) and in other papers. 
Allg. Anat. p. 669. The dllTerence Is most iierceptible In compniiug Ihi' nbien of tt 
anterior and posterior rootf. 

■ Henle, (. e. p. 630. ' Ibid. /. c. p. 631.2. 

Neurologische Notizen ; Frorlep's N. Notlzen, Aug. 1 S37, nnd elsewhere. 
Die specie] 1h Gewebelehre dea Gehororgans. ' Archlv, 183K. Jahreeh.ccl 

' De formatlune granulosl, 4c., tn Valentin, I. e. 



He ettlli them gtlatinom nervoui flbrei, and describes them M pelluoid, flst- 
fibrei, between „^ and ,^ of an inch in breadth, with nuineroui ovnl or round 
nuclei Hrrnngeii at pretty regular disfances on their flat BUrfaces, and more or 
leu elungated and approaching the characters of other nucleus fibres. Some- 
timei also, he wiys, the nerve-fibre k Bplit at its ex.tremitf like the fasciculus of 
flbrO'Ccllular filamenlsin couree of development. 
On tha other hand, Valentin,' who is, on both anatomical and physiological 
grounds, the chief opponent of the notion of a peculiar let of fibres in the 
organic oerres, ngards thone which are so described by others as merely the 
imperfectly -de Tel oped filaments of fine, fibro-uellular tisEue, which are formed 
intuaheaths for the investnieat, not of collections of nervous fibres, as in other 
nerves, but of each nervous iibre separately. These aheaths he believes to be 
continued over the ttbrea from ganglioo-globulea presently to be described. 

The conflicting views mav be probably reconciled according to the explana- 
tion by Volkmann and Bidder,' which haa received the confirmation of E. H. 
Weber. It aeems most probiible that the fibres described by Remak are those 
of the investing inenibrnne of the true sympathetic fibres, as Valetin holds, and 
whiuh, in old frog«,eiaclly resemble thecomroon wavy filaments of fibro-cellular 
tiisue. (E. H. Weber.) But the true sympatlietic fibres are stilt distinct from 
the eercbro-apinal, and wereprobably well dlsceroedhy RoBenthaland Purkinje. 
According to Volkmann and Bidder, they are distinguished by their fineneat, 
(their diameter being constantly about half as great as that of thecerebro-spmal 
nerres,) their palcnets, the absence under all circumstancea of a double contour, 
the very iniall quantity of curd-like contents which they exhibit when decom. 

SOied, and Iheir yellowish-gray colour when they lie in boodles. The dilTerence 
I size between the cerebro-tpinai and the sympathetic fibres is quite diatiact ; 
and though both seta of fibres vary to some extent, there is not nearly a complete 
wrlci ofgrndntiona between them. 

B. Cuaru. The obiiervations of Fontana and of Prevoat and Dnmas, con- 
ftmicd by those of Muller' and others, prove that Ihe nervous fibre is uninter- 
rupted from its central to its peripheral extremity, and that in all that course 
there is no anattomoaia or confusion of substance between any two primitive 
fibrrs— facts proved by both experiment and bight. They have received addi- 
tional confirmation from Kroneaberg* and Valentin,' the latter of whom exa- 
mined particularly the nervous fibres in the recti oculi and other minute mus- 
den of very small animals. 

The microscope has alao materially assisted Volkmann" in proving certain 
iacis respecting the course of nervous fibres which could not have been discerned 
hy ordinary dissection. Such, for instance, is the fact, that in several instances 
flbres proceed for a certain distance from the centres and then, without pnssing 
into the substance of any organ, form loops and return again to the brain or 
spinal cord ; so that dificrent parts of the nervous centres may be supposed to 
be connected by long, nervous fibres, arranged in arches, of which the estrenu- 
tiea are at the centres, and the arcs far external to them. This is the ciue in 
the plexus of the descendens noni with the cervical nerves, through wliich seme 
broneheB of the latter ascend to the brain; and probably also m the arched 
fibres which form the inner border of each optic tract, and the poaterior border 
of the ehiasma ; and in those fibres which experiment haa proved to pro- 
ceed in arches from the posterior to the anterior columns of the cord, through 

> L'eher die Scheiden tier Gnnfftienkugeln, Ac. (Multer'a Arch. 1S39,} anil elsewhere. 

* VerbaltnlsB des Nervua sympnthlcua xii dem iibrigeu Nervenayslcme beim Proschei 
fee. In FroTie|i'>i N. Nottzen, Mure 1842. 

' PhvBlologie, bd. II. 

* De iilexuum nervoniin atnictura, fierol. 183(1, end Mull. Arcb. 1S37, Jabreeb. li. 
' Ueber den Varlaaf. 4c. p. 71. 

* Beob. nnd Befleitionen ueber NenenanaBlomoaen, (Mull. Arch. ISJO, p. filO), and 
Brit, end For. Med. Rev. Vol. XII. p, 239. 



the roots of tlie nerrei.i It lug thiti alio been mnde not improbRble thst tbft'Jj 

two retinm are connected b; dmilar arcs, both FStremities of which itre peri- 
pheral ; nnd perhaps there are Kouie other Bimilar instanceB. 

Bj similnr microscopic tracing:. Vol kmann and Bidder' have settled the impo^ . 
tant fact llint the spnpnthetic nervous fibres form an independent systeni, whote i 
centres are the ganglia. At the chief points of junction of the two syeteiiH ! 
e of the sympathetic fibres (traceable by the characters just described), run f 



towards the spinal cord, others towni'ds the periphery. The proportionals i| 

numbers pnssiug in each direction vary in the different places of connexion. 

n the branches connecting the syinpatlietio with the eighth and ninth spi' 



nerves of the frog, for instance, scarcely any sympathetic fibres proceed centrally 
yet these are the largest of the branches which are commonly described as tu 
origins of the sympathetic system from the spinal cord. On the whole, the 
sympathetic at these points of junction always gives more fibres that it receives. 
It mint therefore have some source of fibres of its own ; and this source il 
round to lie chiefly in the ganglia, both spinal and sympathetic (specially a» 
called,) and, in a less degree, in the cord itself. 

If, it is argued, the sympathetic derived at these parts all its fibres from the 
spinal cord, sucb fibres ought to be found in duly proportionate number in the 
roots of the spinal nerves. But it is not so. In the case of the fourth spinal 
nerve of the frog, for instance, the brxncb uonnecting the sympathetic with it 
is larger than the fourth nerve itself Therefore, since all the fibres of the con- 
necting branch run centrally, they ought, if tliey have their origin from the spinal 
cord, to be found in great numbers in the roots ; but there are fifty times more 
cerebro .spinal than sympathetic fibres in the roots of this fourth nerve. Thf 
sympathetic fibres which pass into its trunlt cannot be traced further than to the 
ganglion on the posterior root. Prom this ganglion, therefore, they probably 
have tlieir origin; and they are deEt!Ded,as those in the other trunks are, chiefly 
to tlie posterior branches of the nerve. The anterior branches also contain sym- 
pathetic fibres, but they are derived, not from the spinal ganglia, but from 
those of the sympathetic itself. 

o. Model of Termination. 1. Peripheral, The arched arrangement of the 
nerrous fibres already mentioned is repeated in the substance of the organs ia 
which they are said to tenoinitu; for, as far as they have been examined, the 
general, if not the constant, mode of termination is as follows ; After repeated 
dirisions into smaller bundles of fibres, the fiisciculi, which consist of from two 
lo six fibres each, form plexuses, whose arrangement bears a general resem- 
blance to that of the elements of the tlssne in which they are placed. These are 
the teraiinal piemiaea.' Each fasciculus of the plexus next hreahs up into iti 
primitive fibres, and each fibre, either after passing over several elementary 
structures of the containing tissue, or, as in the sensitive papilla!, the iris, &c., 
after forming a single narrow loop, returns to the same or an adjoining plexu^ 
and pursuesits way back to the nervoua centre, from which it set out. In other ' 
words, each fibre forms an anastomosis or lerminal loop with another from the 
same or a neighbouring fasciculus. There is thus, strictly speaking, no more 
termination of nerves flian of blood-vessels ; both alike form circles. The cha- 
racters of the fibres are scarcely altered in the substance of the organs receiving 
them : their sheaths become finer, but they are not lost or laid dmea, nor is there 
any fusion of the nervous into the adjacent substance.* 



• L. 

' Valentin, Ueber clan Verlauf, Ac, and In Btit. and For. Med. Rov. Vol. XI. 

' No rnentioii is here made of the cells found near the peripheral dlstriluUiin of the 
nerve* of the higher aeoaen, and supped by yalt^n<in and eomu otbers !□ be Bualognae- 
to the gangUon-globalea at Ibe nervous centres; for they are nat cods tan t elements Iil 
the peri|)beral nerrous alroc lures, and Henle's opinion (Allg. Anat,, (. a&\^ 



J 



But it ie qneationed whether thU.wUch U the only really obierved arrangement, 
be n just nccoiint of the distribution of the minutest elementary nervouH struc- 
tures. Another view of the whole matter must be tnken if it be true thnt those 
which are called the immitive fibres be, as the obaervations of Treviranus,' 
Remak, iind Martio Barry indicate, fasciculi, each contaioing sereral tibrils 
which, though tliey are not discernible in Ibe suhstanee of the tissues, may be 
distributed to their minoteaC parts. If it be so, the real ultimate arrangemeDt 
of the nerves is utterly unknown. There are some imperfect obserratioos re- 
specting the distributian of the minuter fibres, by Schwann' and Reinnk.° But 
it must be admitted as a sirong argument agitinst the distribution of such finer 
branches, that the course of those already described as the ultimate fibres is 
clearly discernible, that they do not nppear to give off branches, and that small 
RB the finer divisions are supposed to be, they would not be less than the Sibrw — 
of many other kinds which can he recognized in their respective tissues. 

2, Central. When the nervous fibres hare passed centripetnlly throug-b ( 
dura mater, the general neurilemma becomes thinner ; and there is a still ^rtl 
reduction both in it nnd in the investment of each fibre when they have peoi 
trated the soperficial layer of the brain orspinal cord. In the same progrew d 
size of the fibres gradually dioiinishes, and the tendency tu assume the \t ' 
form OD the least injury of the investing membrane increases. Having ei 
the brain, whether directly or through the medium of the spinal cord, the fi 
proceed in bundles (which are the coarsely demonstrated fibres of the brain) to- 
wards the cortical lubslance, forming on their way the most intricate plexuses, 
but never anastomosing. Arrived at the cortical substance, the fasciculi form 
plejtuseg among the gray globules exactly comparable with the termioable 
plexuses already described ; and, at the last, the fiisciculi, having bruken up T 
into their component fibres, or very small collections of them, these form loops ■ 
in the cortical substance of the brain like the terminal loops in the substance ofa 
the tissues,* 

The white sobstance of the spinal cord, like that of the brain, is compu 
nro eiillheliuTii -cells covering the layer of ttie exIremitleB of the nerves teems 
bnhle than bd}' bitberto oRered. Tbeir history may be found in hin n-ork, 
esaayi on tbe retina Tefuned to in a Tollowing note. 

■ VermiBchteScbririen, bd.l. p. 129; and Ueitri^, bfi. ii. p.39. 

> Miiller'i Pbyiiologle, bil. ii. 

' ZiiT Mikrosk. Anatomie der N«rven, &c. In raference to the dislrihotioa of f 
nerves In eacb organ il masteufficii to refer ^tierally to Vulenlin'a edit, of tbe Slh vc 
SUmmerlng's Anatomie, and bis treatise Delier den Verliiaf und die letzten Ender 
Nervenj and to Miiller'a and Carpenlir's Physiologies. For parlicalar organa the R 
lovringreferenceamay be sufficient: for the Retina: Hannover, (Miiller'a Archlv, 1B< 
bft. lil.;) Grabe, <tbid. 1140, aod Microsc. Joam. 1X4), p. 71 i) Bidder, (MUU. An 
18410 Remak and Henle, (ibid. 1X40;) Gottache, (Ibid. 1834 jj Hedle, (Atlg. AjmU 
Valenlin, rRepettorlum,bd. V. &c.) RelcbBrt(Miill. Arch. 1841. Jabrmb. which coat^ 
S |;oo(liinsly"'^ofBeveral of the preceding. The Ear: Wharton Jonea,(//ean»f',0rMn4| 
CycL AnaL ;) Pappenhetm, (IJie apeciellH Gewebelebre des Geborargiina j) ViOeitl^ 
(Repertorbim and Ur. and For.Med. Her. Vol. Vlil.p. US. Tbe IViue: Treviroad 
(Bettriige, hfL ii. p. SO.) The SA-ih : VHlentin, (Ueber den Verlauf, Ac. ;) Bant 
(BeilriigB, pp. 108, 161 ;) Bieacbet, (Rechercbes sor lu Structure de la Peaa.) 
MmcUi : Valentin nnd Bucilacb, /. c. Tbe lerminations In tbe ciliary ligament and Itit, 
tbe tongoe, the blood-vessel d, nnd tbe teetb-pul|ia are tiUo dcacrilied by Valentin and 
Bardacb. The Intler shows that In general, though the rule ia not onlversal, the sen^ 
live nerves lurmlnnlB In plexuses, or complex loops, the motor in simple loops. 

' Nearly nil the minute anatomy ol tbe dbres In the nervous centres is due to Ttavl- 
raniu and Valeotin. Tbe arrangement in pleiuiies has been generally confirmed. It 
was first minutely described by Dr. Macartney In 1833, In his " Obaervntions on the Stnic> 
tare and Functions of tbe Nervous System," (sea Abstract In Med. Gazette, vol, xiv. 
p. 842.) Tbe junction of fibres in central loops, first described by Valentin, hai haan 
con firmed by CBriui(Einige Apborismen solder Pbys.desNervenlebenn.Miill. Arch. 183 
andhv Klencke (Ueber die Primltivnervenrasern, Glitt. 1841), bat by no other anatomld 
■ hlmseir has lately spoken very doubtfully of It ( Repertorium, 1840, p. 90), 




^ of 'tM condnned nervous fibres. Bundles of them funn intricate j 

Elexusea witbout anaatomoses, nnd Lave bU a general direction towards the ' 
rain. As far as the microscope c.iu discern, the fibres aa they aaceod get j 
nearer to tiie gray matter, being succ^esaively overlaid by tlioee wliich abul upon j, 
tlie cord higher up thao theniselves; and the cord, as It pasaee fruni below 
upwards, is thuscontinuaily augmented by external layers of tibreB, till it comes 
to tlie medulla oblongata.' 

It is nut probable thut either the brain or the spinal cord contains any fibres 
but Euch as are continuations from those of the several nerves of the body : of 
these tbey form what Valentin has called a condensed collection, 

a. Structure of the Gray Nervoui Svbitajtce. The general character of this 
conslilueot of the nervous centrea is that it is composed of numerous globules, 
called ganglion-globules, from ^ to ^'^ of an inch in diameter, which are usually 
of a spherical or oval I'orin, more or less flattened, and of a reddish colour. Each 
coDtains one or more nuclei with Bubordinate nucleoli, is enclosed in a very^fine 
filamentous inveetment, and is often marked with superficial spots of pigment,* 
These investments or sheatha of the ganglion -globules are, according to Valentin 
Bad others, formed of several strata, uf which the exterior consists of a thin 
layer of fine granular corpuscles, the next ofelougated cells with nuclei, and tha 
most interior and thickest of concentric Iftmellse of very delicate cylindrical fila- 
ments. By its sheath, each ganglion -globule ia iaulated from its neighbours ; 
but by the interchange of fllameuts passing from one sheath to another, the whole 
of the globules are held together in one group, and lie, as il were, imbedded in 
the meshes of a network formed by their investmenls. 

The ganglion -global Oil, which seeui sometimes to lie free in llielr sheaths, so 
that they may be extracted from them, consist mainly of a red or reddish-eraf 
granular material, held together by a clear aoft gelatinous aubstauee; and from 
this, the ganglia and the gray parts of the brain and spinal curd ehiefiy derive 
their charaeterl Stic coloar. 1 he true original form is probably Bpberical, but 
in difierenC situations, either to adapt themselves to the surrounding parts, or 
according to some law of development, they are elongated to an oval or ovate 
form, or are heart-shaped, or kidney-shaped, or angular, or altogether irregulari 
In general, each globule baa but one nucleus with one nucleolus in its wall| 
, but numerous exceptions to this also are found which, as well as the varied 
foruiB of the globules, seem connected with their progress in development, and 
with'their particular offices in each part.' 

D. General Arravgement of' the tvxi Subslances in the Xervmis Centres. The plao 
of arrangement of the fibres in the brain and spinal cord is already described. 
The gray subatance in the central parts of the brain is composed almost entirely 
of ganglion-globules, which deviate from the general character only in beinv 
peculiarly soft, and iuveated with extremely delicate eheaths. 'I'hey are eolleuted 
m small groups in the interstices of the fine vascular netn'ork by which tbs 
gray matter is everywhere traversed; and the layers, ganglia, atid all other 
forms of gray substance, are due to the different modes in which they are aggre- 
gated. On the surface of the cortical aubstanee of the brain, however, another 
Kind of structure ie present, and it is found in smaller quHntity about otiier parta 
of the gray matter: this is a finely granular substance, containing pellucid 

1 The mieroitCDpB dww not confirm the oiiloton of E, H. n'eber, BeUhi^rl, anl 
Grainger that some fibres pass slmightway to the central mibslBnce i>( thr card ; nor 
that, wlilcli Valenlia'a eiperlaients seem to prove, namely, that some of the Qbrea of the 
Botorlor roots wbluli are sent to extensor muscles go at once to the poeterlor columiHt 
and HOme of those uf (be posterior roots to (he anterior column ; neither Joes it afford anjr 
iUastralion of thH leBez or Bssociatfil nenooa acte ; but Ibe positive resnlls of aiperi- 
maots are In Ibeae qaeatioiis much belter evidence tban the negative ones of microseopii 
examl nation. 

* The greater part of Ibis account is Cram Valentin's works. 

> On idl thr^e see Valentin, Heule, and Klencke, In the woiks alteeUj' i\uov«tL. 



I 



•jdmienl or otal Tcrielea, with one or two dark granules in them. In a, 
deeper layer, the»6 Teslcles, instead of being irregularly scattered through tbt 
granular BiLbstaDCC, eeem each to have appropriated to itself a portion of tbt' 
fatter for an independent covering ; nnd from this condition there seems to ba 
a regular gmdalion till, in the yet deeper lai'ers of the cortical substance, ths 
TeslulcBwith their granular coverings, are replaced by perfect ganglion-globulo 
with their filamenlous sheaths.' 

In the pure gray substance of the axis of the spinal cord, the g«nElio] 
globules are arranged in the same manner as in the brain. They are continui 
even below the giving off of the last spinal nerves in a fine cord-like 
which occupies the termination of the canal of the dura mater.* 

The gdnglia, from whatever part of the nervous system lliey are taken, pn 
sent one general plan of structure ; their chief mass is composed of a congerii 
of the ganglion -globules, with which nervous fibres are brought into relatic 
and mingled in various ways. Each ganglionic maes is enveloped by a coverii 
of cellular tissue, continuous with, and analogous to, the neurilemma of t1 
nervous cords that enter into it. The strength of this covering is direct 
proportionate to that of the sheaths of the globules contained within it; ai 
prolougations ii'om the one arc closely interwoven with the fiLiments uf tl 

ITio nervous fibres that enter into the composition of the ganglia are simili 
in structure to those of the sensitive and motor nerves, except that they ai 
finer and their sheaths more delicate. A portion of the fibres which eater ok 
side of a ganglion separate as soon as they have penetrated its substance, am . 
after forming a plexus in its interior, unite again into one or more cords, and 
emerge from the other side in the same manner as they entered. Bat inatbet 
portion do nut pass thus simply ; separating from the plexus in individual 
fibres, or in fasciculi containing each a very few fibres, they wind about in Ita 
interior, and usually near the surface of the ganglion, in the most varied maa- 
ners. In most cases the plexus of fasciculi occupies the central part of ttas. 
ganglion, and the fibres and bundles which compose it maybe natned tl' 
traversing fibres ; the others are, as it were, apiin round the central parts, an 
may be called winding fibrei,' 

Tlic interspaces between the fibres of both kinds are occupied by tbe gai 
g1 ion-globules, which lie variously entwined by small vessels and nervous fibre 
The exact manner of their distribution varies in different ganglia : in some tl 
globules are chiefly arranged around the traversing fibres in tbe centre of tl 
mass; in others they are evenly dispersed throughout, or absent only at li 
very exterior ; in others they are almost all placed at one side. But, liowevi 
the component parts are arranged, the general plan of construction is in i 
ganglia the same. 

Valentin believes that the winding fibres are those which are about to be d 
tributed in the organs to which they are destined, and that the travenii 
plexus-forming fibres are those which are as ^et far from their destination a 
which have to pass through other ganglia, in which tliey also will at last . 
arranged ae winding fibres. There is, he saya, no appearance of fibres generet 
within the ganglia ; none are seen leiiving them but such as are continued frc. 
those which entered them.* Whether they be connected with any fibres of 
peculiar structure is already considered : it is only necessary to add, that so 
of tbe nervesproceeding from ganglia, and having a gray or reddish-gray col< 
very plainly marked, contain ganglion-globules mixed with their fibres. Thi 

' St* Hodle (AIIr. Anot. p. B7T) Bnd Valentin. 

1 Remuk, Biirducb, AmolJ, &c. 

> Vnluulin [Ueber den VerlauF, &c.)j Remak {Froriep's N. Notizen, Aug. 1137% 




f the Bjmpu tl 



tbe cue in tlia connfcting conia of the hutaan cervical ganglia of the Bjmpu | 
thetic, into all of wliich ganglion- globules extend from the ganglin tliemaelvea;' 
audi nervee might indeed be truly calleJ ganglia, for they scarcely differ, except 
in fonn, from the bodies usually bo named. 

Deeelapment. Schwann's account uf the nerve-tube being furmed by the 
coalescing of primary cells, in which the nervous substance is a secondary de- 
posit, is generally received. Henle thinks, however, that the fused cells may 
form only the central axis of the nervous fibre, tliat around this the medullai 
sheath ot Purkinje may be developed, and around this the neurilemma, in tb 
same manner as the sbeath of the muscular fibre isaupposed by Valentin to be 
formed. Of tbe gang! ion- globules, Schwann believed that they were primary 
celts enlarged and containing the peculiar granular gray substance. But 
Henle renders it more probable that those which are called the nuclei of the 
elobules were the primary cells around which the granular substance bus been 
formed ; and lie points out the different structures found in the several layer! 
of the cortical substance of the brain as a repetition of the forms through wbicb 
each ganglion-globule passes. He hence suggests that, tbrousb life, there tnaj > 
be a constant generation of globules on the surface of tbe brain, which may 
gradually move inwards, to replace others that have been destroyed and a' 
gorbed in the deeper layers. Of the muscular and nervous fibrfts, tbe ganglio . 
globules, and the hair, Henle makes, from the view which he has taken of their 
development, a separate class of what he calls coniplkale fibres or cells; of which ' 
the common characters are, that the primary cell, or the axis formed of cells, 
assumes the position of a nucleus, around which a secondary formation is pro- 
duced and is itself invested by an outer sheath. In tbe nerve-fibre, for exampls, 
the axis is tbe series of coalesced cells, the cortical portion is the seer— ^-^ 
formation, and the nuurilemnia is the outer sheath, which holds to the a: 
same position as a cell -membrane does to a nucleus. 

XV. BLOOD-VE SEELS. 

A. Arieriet. After a variety of conflicting and unBatisfactory accounts, 
Henle' seems at length to have discerned such structures in the arteries as ara 
adapted to the functions which experiment shows to be performed by them. 

His account of their general structure is briefly this; 1st. I'hey have an 
epithelial lining,' consisting of a very thin layer of elliptic or rhombic lamellar 
cells, which are sometimes elongated iuto longitudinal spindle-shaped flbreg.* 
2d. There is, immediately external to this, a layer of peculiar tissue, tte 
ttrialed or Jineslrated coat, (corresponding to the ["'erna' cool of the older anft* 
tomiHte,] cousisling of a very thin, rather stiff, and brittle membrane, often 
perforated by numerous round or oval apertures, and bearingpale, flat, very ni 
row fibres, which have, for the most part, a longitudinal direction, and give ii _ 
peculiar delicalely-sCrialed appearance. This coat, which is often morbidlr 
thickened, and, when an artery is contracted, is commonly thrown into longi- 
tudinal folds, is produced by a metamorphosis of tbe epithelium, whose eel 
as their nuclei disappear, coalesce and form a homogeneous membrane, o 

' Valentin, (Ueber den VerlauF. tab, vl.) See atao, on a similar cone In tbe glOBsi 
pbaryn^nl nerve, VolkmBiiu, (Ueber die motoriHcbe Wirkungen, ibc. Miill Archir, 
1840, p. 4HB.] 

■ Ueber die Contructilitat der Gefasee, (Cmiper'a Wocbeiiscbrirt, Mai S8, ]840,) sod 
more fullj In bia Allg. Anat. 

' First deacribed by him in his essay, Ueber die Ausbrellungdea Epitheliums, (Miillei'j' 
Ardiiv, IS-IS.) 

'Remakmid Reichert (MUHer, Arch., 1811, clxixviii.) hold that these a 
Innermoat cells of the leeseU, hut thut within these, and in actual contact with Iha 
blood, tbree is n layer of Hsttoneil round, and polyhedral cells, wUb round, yellowlfbi 
nuclei and nucleoli. On all tbeie obBervalloTn by Henle see Reloherl'a '- -"^ 



h tbeHbrM are Rfterwardi deposited, and which, at Init, m* the MpertuKt 
in it eulnrge, is completely removed, leaving thefihrc8 Tree, (See p. 9). 3d. fn 
lome nrteries there i», next, a coat formed by a. tiiig:]e layer of tongiiudinal 
granular^^ei, flat, and tolerably wido, annlogoUE to a cont which ismuub more 
prominent in the Teins. 4tli. A coat cotnpoied of circular fbret (the Middle or 
elattic roat of moHt former writers, the miaeular coat of Hunter), which formi 
the chiefpart of the arterial irall, and compriaes all that can be torn from it in 
a transverse direction. Its fibres are 6at, clear, and granular, and break with 
abrupt ends. Each of tliem is commooly marked along itg middle by dots scat- 
tered, or regularly arranged in a longitudinal row, or by a narrow streak: 
these are the remains of elongated nuclei, which hare formed ag it were, the 
pattern, according, to which the homogeneous membrane in which they Isr 
has broken up into the flat fibres, ^'he streaks formed of the elongated 
nuclei oflen branch and anastomose, bo as to form that kind of network which 
has led to this coat being mistaken for elastic tissue; whereas it is, in fact, 
the proper contractile coat of the artery, and is, in all respects of develop- 
ment, and microscopic structure, similar to the layers of organic muscle 
in the stomach. See. 5ih. On its exlerior there is a coat of genuine elastic 
tissue (liuu jau»e,t'he elastic coat of Hunter); this exists, however, only in the 
larger arteries, and its thickness, in comparison with that of the preceding, 
diminishes in direct proportion to the sixe of the artery. The direction vf its 
fibres varies greatly in difTerent arteries.' Gth. The eiternal cellular aiat con- 
sisting of common cellular tissue, with longitudinal closely-woven filaments. 

The conclusions from these facts which, as already said, are the first of the 
kind that have accorded with the results of experiment and obserTa.t)on of the 
functions of the arteries, may be expressed in Hunter's words: "From 
account we have given of the suhBtancea which compose an artery, we nn; 
ceive it has two powers, the one elastic and the other muscular. Wt ice 
that the larger arteries are priocipally endowed with the elastic power, and 
smaller with the muscular; that the elastic is always gradually dim inishii 
in the smaller, and the muscular increasing, till, at last, probably, the action 
an artery is almost wholly muscular; yet I think it is nut to be suppoeftd but 
that some degree of elasticity is continued to the extremity of an artery," 

"llie muscular power of an artery acts chiefly in a transverse direction ;. ... 
the elastic power exists almost entirely in the external coat ; the internal cost 

must be the seat of the muscular power Arteries are the conductors and 

disposers of the blood The elastic (power of reaction) is beet fitted for 

sustaining a force applied to it, (such as the motion of the blood given by the 
heart), aod propelling it alon^ the vessel; the muscular power, moat probably, 
is required to assist in continuing that motion, thv. force of the heart being 
partly spent, but certainly was intended to dispoee of the blood when arrived 
at its place of destination."' 

B. Veiiii. The six coats already mentioned include all that are found in the 
blood-vessels; and the distinctions of the vessels of the several ordera depend on 
the proportional quantities of these coats present in each. The veins, according 
to Henie, have, 1st, a lining of epithelium, like that of the arteries; ad, ft 
striated or fenestrated coat, similar to the second in the arteries; 3d, a 1 
ludinally fibrous coat, analogous to that in the arteries, but, in the large . 
formed of several strata, and oflen morbidly thickened ; 4th, a layer, occupi 
the place of the contractile circular-fibred coat of the arteries, but much thii 
than it, and chieS^ or entirely composed of fasciculi of cellular tissue, 
like that of the akin and dartos may be re^rded as contractile; and 5th, 
external cellular coat, with longitudinal fasciculi. The true clasti 
absent. 



if the 11 

-i 



' See enpecially RSuschel, (Di 
1B38;) and Scbwnnn, (Encyclop. Worlerb. 
• Treuliieon the BLoad.&c. 






eil. WUsi 






I. ViatN 




1 

ve I 
»1 I 

he I 



TheTBtTeBexiatinTelDRuf legg than aline in diameter, wbertver their of 

JB to be fulfilled.' They are covered by tbe epitbetium, and congiat of 
like that of fibrous metnbranea, which, ae Hunter observed, prufea that they 
are tiot iluplicatiirt-s of the lining inemhrane. In the larger valvea this tissoB "" 
mined with auine tike that of the striated membrane of the vein. 

Very few concluKionB can yet be drawn from Ibese incts, respecting the active 
functions of the veins. Such as they are, however, they might also be quoted 
from Hunter, who aays, that the veins have nearly the same elaaticitj with the 
arteries; that their muscular (contractile^ power is very considerable ; that the 
former in some degree preserves them in a middle state; and that the latter 
adapts them to tlie various circumstances which require their area to be within 
that state. 

c. Capillaries. However little the miscroscope may have contributed to the 
inowleage of the foregoing part of the circulatory system, it has taught all that 
. U known of this, the more important portion of it. It may indeed be regarded 
M one of its chief honours that it was the means of obtaining the knowledge of 
the last fact essential to the full proof of the circulation of the blood. Harvey 
could only nrove that the arteries carry blood from the heart, and that the 
Teins bring it back ; of the passage from one get of vessels to the other at their 
distal estremiCies be knew nothing, and only in the later part of his researches, 
decided that it was not by the wide channels, which the older writers called 
aaastomotea, but probably through b. parenchyma, in which the blood wns infil- 
trated.' The real mode of transit was first proved by Malpighi,' in 1661, by 
a microscopic examination of the circulation in the distended urinary bladder 
of a frug^. His facts were soon confirnied by many others, and especially bj 
liceuwenhoeek. 

Furm and arrangemenl. It was not, however, till long after this time that 
the general existence of capillaries was admitted; and when it was granted, 
volumes of hypotheses were written about their arrangement, and their variout 
relations to the parta around them.' Of late years the microKCope liiis esti 
blished the truth in far greater simplicity than the imagination had pictured it , 
proving that, to whatever part the blood is sent, it either passes directly from 
arteries to veins (both of very small sise) or flows from one to the other 
through a network of minute canals;' that it never, at least in the healthy 
state, passes from the blood-vessels into any other canals or cavities, or into the 
tissues around them ; and that the only mode of communication between th6 
cavity of the vessels, and any other part of the body, is through the invisibly- 
minute pores, which exist as well in the walls of the capillaries and small ves- 
sels as in all organized tissues.' 

But, though these facts have cleared the way for truth, they have not afforded- 
a deeper insight into the real nature of those processes in which the contenW: 
of the capillaries come into immediate relation with the surrounding partSi 
Marvellous as are the structures revealed by the beautiful art of injection, one 

I Henle, /. -7. 

* Com|)Bre bla Ezerc. do Motu Cordld, p. 56 and p. BO [adit. 11SU), with pi 
the E[iW. Prim, ad J. Rlolangm (p. 105, ej. ed.), and In the Epial. Secnnd. 

» Eplat. Seconda iid J, Dotellum (Da Pulmonlhua, [i. 143), where he descrilws iiolb 
eapilliiriee and the elrcnlatlon lu them. The proof by arllficlal Injection seems to tanTOi^ 
been first obtained by HnrVKy'e friend, Georj^ Eiit (A|Kil. pro clrcul, sang.), but be coDld' 
not trace tbe connexioa whoM exfntence be had proved. 

* Tbe frequent mention of these crealnnsH in physiology will proie bow woll, in rei 
pense for their saflertngs, Ibey deserved the bunom' of a lata emaj by M. Dumeril, " --.^^ 
lea d^couverles faltes dans lea aclenced par I'^lude de I'orgttUlsatlaD dea gretioulUui, (BulS 

du I'Acad. de Mia. 18-lD.) ~^-^ 

* See eapeclnlly Haller, (Elemenla Pbyslologlae, torn. II.) 
> Berre^ calls tbem, not cnplllBrles, but initmteiliate oeaifb. 
' Tbe acute Prochaska whs ainonif the first to eslubliab end Bj)pn:irliile the great rnlaa) 
these facts; see hlaDtsq- Aoat.-Pbys. Orgaaiaml Corp. Hum.. vi-U't,&~ 



CBDDot yet true Ibe p&rticuUr purpoMB thst are served by unjof thennneroui 

varieties of TEiBCulararraDgement; from Swammerilam,' ivho first employed it 
as a means of preparation in 1667, to the present day, it has shown increaKin^ 
wonders of form, but has scarcely afforded a glimpse of the intimate nature of 
nny process.* 

It will therefore be unneceaaarj to enter into all the details of the arrangements 
of the capillaries and small vessels in the seveml organs and tiesuea. The 
eenerat facts are these — that the capillaries compose networks perme;tting the 
interspaces of the proper elements of each organ and tissue ; that the diameters 
of their canals, (which are all of nearly etjualsiie in the saine part,) vary from 
lia i" ijm of an inch, the most cominon size being about jj[„> ; that the nieshei 
generally bear a close relation in form to the predominant disposition of the 
properelements of the tissue, and are in Bonie parts (as the lungs, the choroid, 
and some mucous membranes,) even narrower than the vessels around them, hut 
morecommonly are threeor four times wider J and that, as a general rule, the 
more active the functions of a part, (especially if it be an organ of secretion,} 
the closer is its network of capillaries. 

2. Structure. The capillaries hate distinct walls, and are not mere channels 
drilled in the tissues around them. In some parts they seem to constitute the 
main tissue, as in the pia mater, which is an irregular vascular network with a 
few cells scattered in its meshes, and the smallust possible quantity of cellular 
tissue, the vessels in the pulpy membrane of the cochlea of birds, and, as 
Mr, Bowman has lately discovered,' the corpora Malpighiana; in others they 
are separable from the soft surrounding tissues, as in the choroid, iris, and 
retina; and in all parts of which the tissues around them are well distinguished 
by colour and compactness, the walls of the capillaries are plainly discernible. 
The only question now is concerning the tissues which compose them. 

According to Henle,' the finest vessels are composed of a completely struc- 
tureless membrane, in which no fibres or strix are ever discernible, but which 
bears minute oval corpuscles, the persistent nuclei of the cells from which the 
capillaries are formed ; they are placed longitudinally upon the vessels, and are 
arranged in one, or two, or alternate, rows. This is named the primary niucti/ar 
membrane, because it appears to be the direct product of the primary cell, or 
cells from which the capillary vessel is formed, and because, in various develop- 
ment, it esists in the vessels of every kind. In vessels of a size just larger than 
the capillaries, the nuclei of the primary membrane are considerably elongated; 
and there are added an inner layer of epithelium-cells and an outer layer of 
pellucid membrane, bearing elongated, transverse cell-nuclei. The latter repre- 
sents an early stage of the circularly-fibrous coat of the larger arteries. It ia 
ftam these elongated, longitudinal, and transverse nuclei.that vessels of this size 
acquire the appearance from which Schwann,* and Valentin' deduced that they 

' See his life by Boerbaave, and a communication to the Royal Society In 10^2. 

' The most beautiful delineations of the minute vessels are those bj Maacagai, (Pro- 
dromo della grande Anelomia; Berres, (AnaL Miciosc Corp Ham ;) anil Arnold in 
bis recent great work on Analomy, Tbe differencet of Brrangement are much less in tbo 
capillaries tbenisi^lres than In tbe small reaiels |>recedjiig and rollanlng them ; it Is to 
tbese oluoe tbul tbe descriptions which nuthoia give of urburesceut, [ilumose, tufted, and 









\KrBUBe(VermischlBBeD 
rom ^ to 



Miill. Arcb. 1637, and Brit & For Med. Rev., vol.vi.), 
not mots than from ^^ to „i|^ and olbera vary ing 
. , and organic mtucle ; l>ut bin ubaervationa have not 
'ally connrmed. On the whole, bovever, tbere is sufficient evidence that In 
some parta, such aa tbe brain, there are a few vessels not large enough to tratiamil the 
blood-glabiiles, (see Henle, /. c. 471 ; and Wngner, Lebrbncb, p. 186.) 

• Ou Ibe Malpigblan Bodies, &C., Pblloiopb. Trans. 1843, and Medical Gazette, 
September, 1S43. 

• Allg. Anat. 4!)l. ° Bncyclui). Worterb. art. GefoMe. 
' RppBrlorium, bd. ii. 



43 

hare transverae fibres, and the latter that they poeaeBS both clastic and cellulaf | 
tisBue. Dr. Martin Barry, probabW in theaarae structures, dLacerns compound I 
double-spirai filaments wound Bpirallv around the vessels.' 

3. Fimcthni. The knowledge of the mode of droulatioo in the capillai-iea 
IB entirely due to the microscope, but it must be admitted, that except in 
Dr. Barrf'i account of tlieir structure, there is no anatomical confirmution of 
that which other modes of ohaerration have sliowD, namely, that they and the 
small arteries and veins are not at all times merely passive tubes, but occasion- 
ally exercise a power of regulating the flow of bloou through them. 

Underordinarycircumslancea the blood moves throug-h the Bystemic capil- 
laries in an even streaai, at an average rate of an ineh in a minute and a half, 
and through the pulmonic system, at the rate of about five inches in the same 
time.' But many circumstutices iufluence the diameter of the capillaries, and 
the motion of the blood in them. Besides the pathological cbanges which they 
undergo, the small arteries and capillaries are seen to be uontracted by cold,* and 
by warmth to be slightly enlarged ; under the influence of certain irritants also, 
such as capsicum, or an essential oil, they contract, and again, immediately 
after, dilate ;• which fully confirms what general obeervations had made probable, 
namely, that during life a power is exerted, by which the small vessels, chang- 
ing their diameter, can control the passage of their contents. And, in like man- 
ner, some conSrmation has been afforded to the evidence from experiiueut, that 
this power is exerted under the influence of the nerves; for an anatomical con- 
nection between the latter and the small vessels has been proved by Purbinje, 
Valentin,^ Remak," Henle,' and others, who have seen fine nervous filaments 
on the walls of the cerebral and other blood-veEsels of less than ^ of an inch ia 
diameter. 



observed bf Halier, SpalUnzani, and others, but its importance was not appre. 
ciated by them. From M. Poiseuille'a' observations, confirmed and extended by 
B. H. Weber," Gluge," Wagner," and Ascherson" (who li.ts seen the same an. 
pearance in mammalia,) it appears that the stream of blood flows most rapidly 
in the axis of the capillary vessel, and that its velocity gradually diminishes to- 

' Proceetlinga of the Rofsl Society, Jan. 6, 1 S43. 

• These cnlculalions wtre mado by Hules, (Sluticka, toL li.) Those by E. H. Weber 
and bla brother (Miiller'a Archil, 183H, p. i50),mnke the velocity equnl to about IJlnch 
per minate. In either case the rcanll aeenu incoiiaislent with the rale at which [luidonB 
and other substances are proved, by the experiments of Hering and Mr. J. Bliike, to be 
carrieil wilb the blood; but tbe length of capillary tube through which each globule 
boa to pais is extremely small, and In the larger tubes (ha current in much more rapid. 
Perliapaalio tbe globules move more slowly (ban the plaama ; if so, the conclusionv fioiB 
the mleroscope muit be deceptive. 

■ Schwann and otberi,can(irniingHaatlngi. 

*Seee]<peclallTDr. C.J.B. WlUlama, (Gutetonlan Lectureg, Med. Gaz. IN41.) Mi 
of the previous olueriatlona by Knltenbninner, Wedtmeyur, Ijonting*, &c, are neai 
valnelaiii, since II is prohabte that tbe subatances they employed might ehamicully M 
the phjalcal condition of (he hlood-vesaeis and the ailjacent tissues. 

" Uober den Verlouf dar Nerven, p. la. 

' Ob». anat e( micros, de system, nerrasi atnicturl. ' Allg. Anat p. 61 ] 

' Rrcb. aui led causes du mouvemenl duaangdans les vaisreaux cuiiilliiires, (Aiui. 
Sc. NsLlitae.) 

• Miilier'a Archlv, 1837; and Brit, and For. Med. Rev. Vol. IV. 

" Sur la couche Inerte liet vaisseoox capillftiros. (Ann. des Sc. Nal. Jsn. 18aP.) 

" Nnchlmge zur vergl. Phys. des Blutes. 

" Miiller'd Archiv, 1S3T, and Brit, and For. Med. Rev. Vol. VI. p. 21B. Among m 
deductions which niaj be drawn from (his fact of tbe blood being st reat near the w 
of tbe veimeh, is that the cnpilinrlei do not exerciae n coiislanl force in propalling it 
they did the part next (ho wall should move must rapidly. 



warJattieclrcuTaference, till, to immediate contact with the whIIs, then im layer 
which iB perfectly still. The breadth of this layer, which is the simple result 
of the adhesion oi the blood to the walls of the vessels, is usually from J to ^ of 
that of the whole stream, and is the greater the slower the general current is. 
Its existence and the different relations of the other piirts of the stream are 
discerned by the observation of the blood -corpuscles. Tlie perfect ones com- 
monly occupy the middle of the stream, surrounded by the lyiiiph-corpuscleB, 
which move ten or more times slower than those in tbe axis stream. These 
corpuscles again are surrounded by tbe motionless layer, into which if any 
globules are forced, they move very slowly, and, if they come near to the waif, 
remain for a time quite stationary.' 

The fact that the purpose to which the capillaries are habitually subservient 
is only the passive one of conveying blood close to those pnrts of the body 
which either grow or secrete, renders the vascularity or n on- vascularity of a 
tissue a matter of less interest than it used to be; for it is proved that if a part 
be only able to imbibe the fluid portion of tbe blood from an adjacent vessel, it 
nourishes itself as completely, and after the same method, as one whose sub- 
stance is tritversed by numerous eapillaries. The extra- vascular tissues, as they 
are usually called, that is, those in whose snbstance neither injection nor the 
microscope has yet revealed any blood-vessels, and which derive their nutritive 
materials from the blood flowio"' in adjacent tissues, are the crystalline lens, 
epidermis, epithelium, and all forms of cuticle, hair, nails, enamel and dentine 
of teeth, ana the analogous structures of feathers, hoofs, &c. To the list of 
vascular tissues the microscope and the improved art of injecting have added 
the cornea,* the anterior part of the capsule of the lens,* the membrane uf the 
aqueous humour,' the hyaloid membrane,' the articular^ and other cnrtilages,T 
the tendons," the elastic tissue,' and even the densest bones. 

Jieutlopmait. Schwann's account'^ has been already mentioned, and Valenlin't" 
is, on the whole, confirmatory of it. But the direct observation of the process 
is estremely difficult; aod Reichert" thinks it more probable that thecapillaries 
are developed as the larger vessels of the embryo — those of the area vatculosa, for 
example — are; namely, that cells accumulate in lines or heaps, of which the 
central cells gradually assume the character of blood -corpuscles, while the pe~ 
ripherdl ones, as soon as the blood begins to move through them, unite to form 
the wall of the blood-vessel. The relations in development which the coats 

' II is probable that tbe local influence of cold In mnklng the stilllayer wldei, and in 
retarding the titeaia at blood. Is du« as mncb to Bome pbyaical inBuence as lo the coD- 
tractian uf the vessels, for M. P. could neier discern the latter: he tliereCore refers tha 
retardation to the welt-known rule that tbe qusiitily of the same fluid transmitted in a. 
given Ume by a cnpillary lube It, wilbln certain limits, directly proportluncil to its tempe- 
mtnre. He hits piavad niaa that the Influence of cold la not merely local ; but tliatwbea 
it is applied la nriy pail, the copillary rircolation Is slightly letarded la all ; perhaps 
throuffh Ihe reflex influence ot tbs cold ujion the heart. 

» Homer, in Brit, and For. Med. Rev., vol. ii. 235, ifeCi Bsrres, (. c.,t. xli, f. 

' Schroeder van der Kolk, Over choroiditis ala oorzaak van Glaucoma, in tha Verhi 
van bet OenooticbDp ..-. te Amsterdam, 1841. 

* Schroeder van der Kolk, /. e. 
< Beriei (l. c. PI. xiv.) ; Dahymple (in Tyrrell on Diseaaei of (he E]e.) 1'be moat 

perfect Injection Is described by 8. Van der Kolk, I. c. See, how'ver. For evidence against 
these Injactiona, Mr. Toynbee's paper In the Philos, Trans. 1841, p. 159, " Researches 
tending," &c. 

* Listen, Medico-Chirorglcal Trans, v. 23. 
T Fremery, Miillef*a Physiologle, i. 2S3, jkc. ■ J. P. Medicsl Gazette, tBi 

* Berre:!, Dcrlliugei, Uc. Bui this U rRlber doubtful ; the vesi^els were perhnps 
proper contracllie coat of tbe arteries. 

" See paj(e 8. 

>■ Uebor die Entwlck. dn Mnskel- dei Nerven- und des Btulgi-riiMsyBlt'ms, fMul 
Archlv, IS40.) 
"Mli""-'- •■cU», I8tl. Jnhresb. 



iu^H 




epithelium-eel la nre constantly developed from the gubjncent n 
fenestrated in em brfine proceedi from n coalesced layer cifepltbcliui 
ftflerwHriiB broken up Bccording to the puttern of thenuclei formed onitj tha 
fibres of the longitudinal fibrous cuHt are formed from the elongated longitudi- 
nal nuclei of the pricDarfriJeiiibrane; the circular fibrous coat IB formed from it 
cytoblastema divided into flat fibres on the model of nuclei formed in it ; and 
t^hc elastic and flbro-cellular coats are produced as those tissues 
parts of the body. 



XVI. LYMPHATICS AlfD I.ACTEAI.S. 

General Structure and Jrrangemevt of the Vessrla, The researches of Panizza,' 
confirming; those of Cruickshank, Mascagni, Pohmann, and others, have estab- 
lished that in the tissues generally the lymphatic vessels arise from clusely- 
mcshed networks which are interspersed among the proper elements of each 
part, and which, like those of the capillarj blood -vessels, vary in the size both 
of the canals and of the spaces which they enclose. I'lie diflSculty, however, 
of learning the exact size of these canals is even greater than with the bloud- 
vessels, because of the remarkable yielding of their walls. 

There are still several organs and tissues in which iio lymphatics have beea 
discovered ; such arc the brnin and spinal cord,' the bones,^ the cartilages, the 
dense tendons, the eye,* the placenta, the umbilical cord,' and the ntembranes 
of the ovum, and all those into which blood-vessels have not been traced. 

The structure of the larger lacteals and lymphatics is very similar to that of 
the veins. They are lined by an epithelium like that in the blood-vessels ; next 
externally to this is a layer of nearly longitudinal fibres of a character inter- 
mediate between those of cellular tissue and the granular fibres of the arterial 
contractile coat; and around this is a layer of fibres of cellular tissue, which 
have a circular arrangement, and are connected with those of the next adjacent 
tissue.' The minutest lymphatics seem to be destitute of valves ; but valves are 
discernible in those of less than one third of n line in diameter, and have the 
same structure as those of the veins.' The minutest lacteals in the villi consist 
of a single membrane with elongated celt-nuclei, corresponding to the longitu- 
dinal fibrous membrane of the veins, but not lined by epithelium.' 

2. Abiorbenl Glanili. In the lymphatic and lacteal glands, the walla of the 
large vessels of which they are mainly composed are traversed by a dense net- 
work of capillary blood-vessels ; a circumstance which affords some confirma- 
tion to the belief that something passes bj* a kind of secretion from the blond 
to the lymph and chyle in them, by which the latter becomes more charged 
with fibrio, and by which the development of the corpuscles is forwarded. 

The question whether, in man, the lymphatics and small veins anastomose 
either in the glands or near their origins, still exists. They cert.iinly anasto- 
mose in the latter situation in amphibia and fish," but the microscope has added 

' Oaeerrtizioni ontn 

' Arnold (Icones t 
coieringi of these org 
were doubtrnl. 

' Cruickstannk and 
their euccesB it doubtr 

* Ma«agni (Frodiomo) deacrlbes 
thing as a lympbslic. 

* See Miiller's Pbyslologie, 1. p. 2f 

* Heule. A11g;em. Aunt. p. £51. 
T Valentin, Reperlorium, 1B3T. ■ Henle, (. c. 

* Sea e!i)ecinllj' Hyrll, Med. Jabrbuch, des Oeslerreioh. Stiiotcs, bJ. 



I 

I 



-GgioloRiche. 
1.) givei odmirabla figures 
iltg of bis attempts to injeci oioerB i 

belleted tbey had injected lymphatics in bone ; but 

in the eye ; but he was («o apt to n^rd ereTj I 

I Fohmann's auppased injections. 



3. FiUi. The bodies to which this name should be esoiusively applied ara 
fcated \a the imall iatestineg only, and are peculiarly Iht: orgun^for tlie ab- 
■orption of the chyle. They are delicate vascular processes of the miiuou* 
membrane, from a quarter of a line to a Hoe and a half in length,* of which 
about tweoty-flve are set on every squAre line of lurface.' They ?ary in form 
according as the veueU they contain are empty or full of chyle: in the former 
case they are flat, and pointed at their Eummits; in the latter they are cylin- 
drical or clarate,* Into the base of each there enters a single lacteal vessel, 
which, after passing along the middle, cndg either in a blind, slightly swollen 
extremity, or, as Krause* and Valentin' think, in a network. In some villi, 
also, there are two such vessels, which pass along opposite borders and terminate 
without anastomosing.'' The walls of each villus are traversed by a very ddicatc 
network of blood-vessels funned of from three to fire minute arteries, which, 
after variously dividing and anastomosing, are continued into one or two veins 
which descend along the villus to the vessels of the submucous tissue,' Each 
villus is farther invested bv a very delicate sheath of epithelium, which is fre- 
quently, perhaps after each completed digestion, shed. 

Hese hcU regarding the structure of the parts of the absorbent system do 
not at all illustrate their mode of operation. The lacteals have not open ori- 
fices in the villi ; they probably derive their appearance of terminal apertures 
from the cells which compose the epiihelium over them ; they probably, there- 
fore, net by imbibition through their porous walls. But it is to be observed 
that they do not lie next to the fluid which they absorb; they are covered by 
n layer of very vascular mucous membrane and hy a aheath of epiihelium. 
Valentin' was henue led to suggest that since the blood-vessels in a villus hul ' 
nearly the same relation to the lacteal as in a secernent gland they do to 
extremity of the duct, and since in absorption the material from the intestineft^ 
must pass by the blood-vessels to enter the lacteal, it is therefore probable that 
the chyle is not immediately transferred from the intestine to the lacteal, but 
is, as It were, secreted into it through the medium of the blood-vessels. Mr. 
Goodsir'° has since made it ver^ probable that the agents by which the chyle ia 
absorbed are a layer of cells, whicb are developed each time the act is performed, 
beneath the covering of the villus, and from whicli the chyle, after some degree 
of elaboration, is discharged by their rupture into or immediately around the 
lacteal vessels. 

With regard to the lymphatics of |the peripheral network, Dr. Carpenteri' 
has made it highly probable that they do not imbibe all fluids indifferently, 
but that their of&ce is to absorb the nutritious products of the Kcmidari/ dige»- 
tioa; that sort of digestiuD which, as Dr. Prout says, is carried on in nit 
parts of the body, and by means of which substances are appropriated for nutri- 
tion bolh from the dead and decomposed elements of all the tissues, and from 
materials deposited in store for reabsorption, as the fnt of hybemating animals. 

Experiments have rendered it, on the whole, probable that the coats of the 
larger Ivmphatics have vital contractility, and their microscopic structure is 
favorable to this view. Without such a power the motion of fluid in them it 

' Sea Miillei's, /, c. p. 238. 'IbiJ. /. c. 

' Lieberkuhn, Diss, du Fahricl et Actione Villotum, 1 782. 

* They present many other form:! in auimsls ; but these ai^em to be Ifau only ones that 



by 
tlW^H 



' Vermlscbte Beobachtungen, (Mill 
• Miillei's Arcbiv, 183B. 
' Lieberkuhn (/. c), Doellinger {Di 
' T)e funcliane nervornm, Ac. p. I'l^. 
■' On the Slructura of the Villi, &c. Edinb. Phili 
For. Med, Ror. OcLlMa. 
'■ Princ'- ' " wmn Phfiiology. p. 331. 



Arcbiv, ISST.) 

' Henle, Symbols oA Anat 

Is sanKutaels iiub villla ineu 



. Journ., July, 1842; ani! Or. and 





I inexplicable i with it, no other is neccssar; ; for the vaWei, extending u thef 

'it branches, must rtnder the whole force of the contraction 
of each aeginent efBcient to the propulsion of Huid into the segment above it. 

XVII. SECERNENT GLANDS. 
Many of the general rules of ^landujar structure laid down by Malpigbi ' 
nnd Miiller' are deduced from microscopic observation, or, at least, tbey are 
settled by it, for the objects illustrHtiie of them do not all lie bej'ond the field 
of ordinary TJsion. Of these general rulei, the chief are: lat. That a general 
unity of plan prevails in the seemingly manifold varieties of glandular struc- 
ture ia the different organs and classes of animals : 2d, That all secretory 
glands are composed of tubes opening on a free surface and either simple, or 
variously ramified so aa to present in a small solid space a very great extent of 
surface for secretion : 3d, That, while the excretory end of the gland-duct opens 
on a free surface, its oppuiite or secretory end is always closed : 4tb, That ag- 
gregations of these blind ends of a ramified gland-duct form the ncini which 
were long supposed to be the proper agents of secretion : 5th, 1'bat tliere is 
no open communication between gland-ducts and other vessels, and that the 
blood-vessels do not open into the ducts or acini, but ramify in a capillary net- 
work in their walls and interspaces, and there supply the materials of the secre- 

Recent observations by Henle, Krause, and others, render it very probable 
that some of these general rules, tbough true as far as they go, require to be 
modified or added to. Tliere are organs which may be strictly called glands, 
yet have nut tubes opening constantly on a free surface, but open thus only at 
particular times, by a kind of dehiscence. Such are the Peyer'e and solitary 
elands of the small intestines, first well described by Biibm,' and since by 
Krause ' and Henle ;' and these mav be tahen as a type of a numerous class of 
similar bodies which occur constantly, or at particular times, in the substance 
of all mucous membranes.' £uhm described the Peyer's and solitary bodies aa 
simple sacculi beneath the mucous membrane, without external orifices, con- 
taining a fiuid rendered opaque by a number of minute white granules and cells, 
and surrounded by what he called a coroTta of tubules, which had no commu- 
nication with their cavities. Krause, however, believed that he succeeded in in- 
jecting some of the sacculi througli these tubules; and thus, tbough by an error, 
supplied the first step to that which Henle has generalized with other facts of 
the like kind in the very probable tlieory, that all the sacculi of this kind 
are secretory organs, which are closed till the secretion within them is matured, 
and then, by an absorption or bursting of their Cnely-membranous walls, open 
a cumin It nication with the suriace of the membrane over tbem, and thus dis- 
charge their contents. 

If it be admitted that any organ should be regarded as a gland which ab- 
stracts materials from the blood, and instead of appropriating them to its own 
nutrition, discharges llieni externally, or into some cavity, then, many organs 
not hitherto regarded as secernent glands mav take their place in this class; 
such u the ovaries, and the su-called vascular glands, which probably elaborate 

' Epialtda da glandulanun coniimilimnqae psitiam itructnriL. 

' Db gisncjularum gtiucliirft peiiitiori. 

' De Rtnnduluriuii InleatidoUiun atructilil penltiort, 1S3S ; see also Bril. and For. 
Med. Kev. Vol. I. |i. £21. 

' Vermiacbtii Beubachtungen, (Miiller'a Arcbiv, 1831.) 

' M liner's Archiv, 1H3H, bfcii. note; nnd AUg. Anal. 

' Leiut, who is quotnl by tlenlo witb Judt prnise Tui bia excellent inveatigalioni of 
e]>itbulia, ilescribes numeroua glands withoutducte in Ibe jtharynx uud usoiibagiia, (Des 
Rlandes muqueusea, &c. In Joum. Hebdomad eire, 1S33, t. l^,) To Ibis clau i ■ 
be referreil the so-called mucoua or lenticular glondnoccasionaliy met witb in the 
nrlnarr bladder, drc. 



I 



■ome fluid uid add it to tlie blood in their vegselfi, or pecoliiirly alter the blood 
Bs it circulateB through them. The Dearies, indeed, may ht taken as n type of 
the glands which have not pennBnently open ducts; for theycootiiin numerous 
cells, tlie Oranliiin vesicles, imbedded in their stroiun, which, at the time iif con- 
ception, huretinff through their enveloping niembraneB,OBcape into the oviduct, 
and leave behind thcni empty sacs. Juet so it is also with the Peyer's glanda, 
and all the others of that cfass; in the place of which we often find foesie, the 
remaini of the »accuU or vesicles that have recently burst through the mucous 
mcuibrane, with whose surface their interior thus hecoincs continuous. 

The proper morphihekul element of a gland, then, seenis to be a sacculus or 
vesicle, elaborating witTiin itself or attracting into its cavity the material of 
secretion, and discharging it through either an occasional or a permanent orifice 
or duct. These primary vesiclei fas Henle ' names tlicm) are probably primary 
cells more or less metamorphosed. The walls of the smallest among them are 
formed of a translucent, structureless membrane ; those of the largest consist 
of several layers of elongated nuclei and filaments of cellular tissue, arranged 
in concentric circles around them, and are sometimes lined fay an epithelium. 
These additions, it is presumed, are efi^ected by Che development of nuclei and 
ceils from the primary cell-wall ; as in the blood-vessels the epithelium and the 
striated and flbroos coats are produced from the primary vascular membrane. 
The structure of the larger permanent gland-ducts also, when any can be se- 
parated from the vesicles, is very analogous to that of the blood-vessels, and is 
perhaps the result of similar phases of development. They consist of an inter- 
nal layer of epithelium-cells (generally like those of the adjacent membrane), 
surrounded, itnt, by a layer of longitudinal fibres similar to those of organic 
muscle, next by a much thinner, and not alwavs discernible, layer of circular 
fibres of the same kind, and lastly by a layer ol" cellular tissue.' 

According to the mode in which the primary gland-resides arrange them- 
selves, three different forms of gUnda with permanent orifices may, according 
to Henle,' be produced. I st. The cloied tubular glandt, which are formed of a 
single elongated vesicle, or in which a number of vesicles may be supposed to 
have arranged Ihemttelves in one line, and then to have all opened into one 
another by theirappoaed portions, except the lowest, which baa remained closed 
at one end, and the one nearest Ibe surface which has opened externally. Such 
are the Lieberkuhnian and tubular glands of Ihe intestines, and the simple tubn- 
larglands of the stomach; mere tubes, like single gland-vesicles elongated to dif- 
ferent depths, with walls composedof a tube of structureless membrane, opening 
permanently on the mucous surface, and closed at their opposite ends. Such 
also, though rendered morecoiuples by the attachment of vesicles along their 
sides, are the Meibomian glands; and such, elongated and grown tortuous, are 
the perspiratory and ceruminuus glands. 2d, The aggregated glands, in which, 
a number of vesicles arranged in groups have become so connected by a kind of 
fusion of their adjacent walls, that only a small portion of the membrane of each 
remains, and they form one cavity, with numerous recesses from its inner cir- 
cumference. Such are all those commonly called mucous glands (as those of 
the lips, trachea, vagina, Stc.) ; and the tonsils, lachrymal, Brunnian, salivary, 
mammary, and Cowper's glands, the pancreas and prostate; which differ oulj 
in secondary points of structure, such a« the arrangement of their evcretory 

■ All^^emelne Anstomie, p. 821, e. a, * L.c,, |>. 906. 

■The dBicrlptioni of the muscular libres are drown chii'fly from Iheglnnd-ductaof lar^O 
nnlmals ; SQcb as the uiDtera and bile-ducts ol sheep and haraea. (See especially Meyer, 
De muBculls in ductibuB eff. gland., diaa. Innug., Bcrol. 1N31 ; and In Protlep's N. Nollzen 
Mara IMS; and Henip, Allg. Anat. p. VAi.) The aame ilructures are presomed to ailst 
in man rather froin Hnelogy and from pnthologlcsl facta Ihsii from actual obsenation. 
Toiirtunl has dlicavered true nuigcalnr fibres in an hypertrophled human dj ' 
kelfiuem im erwfiterten Ilarnlellar, &c., Miillcr's Archiv, 1S40;} but 1 
detailed accounts ol the muscular costs of other human gland-duct^. 






» 



49 



ducts, and the mode in which the primary lobuUs ur simplest groups of gland- 
TFaioles are connected together by nbro-cellular tissue, and supplied bj blood- 
TBBselB. The amalleil branches of the gland-duels sometimea run into the cen- 
tral cavity of the group of vesicles, which thus all open into it : sometiuiea the 
groups, ur primary 1 oh u lea, are tet upon the extremities or by the sides of the 
ducts I but whatever secondary arrangement there may be, all have the same 
essential chiirncter of rounded groups of g land -vea idea opening by a common 
central cavity into minnte ducta. 3d, The retkulaled glands, auch as the kid. 
neys and testicles, which consist of tubes of a transparent and structureless 
bomogcneous membrane, the tnembrana propria,' probably formed by the elonga- 
tion and anastomosis of cells, like the blood-vessels, or the Haversian canals in 
bone, and like them, connected in a network, and seldom or never ending in a 

Whether the gland be a vesicle which only once ur occasionally opens, or 
one which, perhaps after sundry metamorphoses, has a permanent commuaica- 
tion by ducts with the external surface, the mode of aecretion seems to be the 
aame. It is, however, still a question (and one which the microacope will not 
decide,) whether the fluid separated by the vesicles be always already formed 
in the blood, or whether it be not in some cases elaborated and transformed in 
tliein. iProbahly there is not one rule for all glands. In certain secretions 
the microacope detects conatituenta which could not have been aeparaled as such 
front the blood, namelv, globulea and corpuscles of different kinds, which in- 
dicate that the fluid separated had the character rather of a cytoblastema than 
Af a dead matter. 

Tn those secreted fluids which serve especially or solely for the purification 
of the blood, and are therefore more peculiarly excretion's, auch as the bile 
and (he urine, there appear to be, during health, no corpuscles. But in those 
which after their discharge have to serve some special office in the economy it 
is very usual to find cells either perfect or in various stages of development. 
Uenle has treated at aome length of these endogcnuut cells. It may eufflce to 
say of them, that Ihey sometimes constitute the essential part of the secretion, 
M in tlie testicles, where they either become or generate witliin themselves 
the seminal filaments or animalcules i' the ovaries, where tiiey become the 
geruiinal veaicles ; the matumary glands, where they are the peculiar niilk-c 
puaclee ; the gastric glands, where they contaio dif""'"— "■■■■* '- "" 



thei 



e fluid, In other c! 



form an epithelium to line the ^land-vesicles and tubules; in others, 

hout any evident purpose, they are discharged from the gland-ducts or fill 

" ■ ■■■ ' " of the so-called mucus-corpuscles; in others they 



the preceding account 



it is plainly 
1. In both 



not possible to draw a 



t lin 



ap^e. 

betwei 

blood may work in itself those changes which are commonly regarded 
raclertalic of life. Neither can expulsion from the scat of their production be 
regarded as peculiar to secreted auHtances ; fur the elements of many epithelia 
remain attaclied only a little longer than the corpuacles of some secretions, and 
the attachment of aome of them is perhaps even shorter, as, for iualance, of 
the epithelium-cell a of the stomach in comparison with the animalcule-genera- 
tiugcella of the semen.' 

' The batenieHf membrane o( Mr. Bowman, (Cjcl. of Aiiat. art. Mucooa Membranti,) 
who lusiiectB UiHt ■ timllur membrDnH also liei beneath all epitbella. 

' See aome observations Illustrative of ihle hj M, LallemDOtl, in ibe Comptei Kendoi, 
1811, und Edlo. Meil. and Surg. Juuin., 1841, Seealao Martin Bnrry, f.c.Hiid Kolliker 
' tieb. dm Vfiaea der Saamenlblt-re, (Fror. N. Nolii, Juli, 1841.) 

' Tile whole qaestloa of lecretloo is admirably treated by Mr. Goodsirla bh essay " On 
ttie Dlllmale lecretlng; alnictnre," Sic, in the Trsna. of Ibe Roy- Siic. of Ediiibuigh ; 
wblch, unTorlunalely, did not come under notice (III it was publinb ■"'''' 
For. Me<l. Rei. of lUe (iresent month. 



I 
I 
I 
I 




ITnder this name maj be clasaed the thfnma a*d Ihrrokl glands, the rmd — 
capsule* »nil the spleen, wbich, is Henle' vetl lajs, '" a^rife chiefly in this, 
that both their minnte Krncture and their phjiiolo^caL import are at preuot 
totally uakoown." Il mar suffice, therefore, Eu refer to the chief works in 
which there arc origiual ijcscriptioiis of th«r aunute fltrncture.* 

SIX. ERKCTILE TISETE. ^M 

This might perhapc justly bare had iU place vith the description nf the or- ^| 
gam of circulatiun, lince the only funcrioD which it discharges seems to be 
chiefly due to the peculiar arrangement of its blood-vcMelji. The parts in 
which it is found, however, are lufficiently similar in their characters to form 
a separate claM: they are the penis, the clitoris, and, perhaps, the nipples. 
The first has been so much more examined than the others that the descrip- 
tion of its stmctnre is taken u the type of theirs.' 

Independently of its blood -teasels, the erectile tissue of the penis is composed o( 
■ network of corda and bands, which form a multitude of freelr-communicatiog 
cells, of Tarious shapes. They are chiefly derived from the fibrous envelope of 
the penis, from which thev pass on either side inwards, connecting the septum 
with the outer sheath. 1 he substance of these cords and bands is traversed bv 
the arteries of the erectile tissue, which usually run very tortuouslr within 
Ihem: the spaces or cells between the cords and bands are ocenpied by the 
Tcioi. Each cord or band has in its interior an artery of a aije proportionate 
toitsowo: where one seems to branch, the artery within it also divides, and 
•ends a branch loits division; and where the bands and cords unite, the arteries 
within them also unite and anastomose. The (erminalious of the arteries upen 
in an uncertain manner from the cords which contain Ihem into the veins which 
are placed in the interspaces of the cords and hands, and of which the Utter, 
since they are covered by the lining venous menbrcine, mar he said to form 
the walls. 

Tliese bands and conls which form, iis it were, the skeleton of the erectile 
tissues, are dense structures, composed of several diflerent tissues. Frnio its 
surface inwards eachconsistsof the following layers: Ut, a portion of Ihecom- 
mon lining membrane of the venous system, which is here, as elsewhere, in con- 
tact with the venous blood ; 2d, a mixed Inyer of elastic and fibro-cellular (issue, 
which corresponds to the outer wall of the vein or venous space ; 3d, a Uyer 
of fasciculated fibres, exactly resembling those of organic muscle, and usually 

■ Allg. AnaL p. e»6. 

* On all ef them, Berres, (Anat Micros. ;) Mdller, ( Pbysiologie, hS, i. anil Arcbiv, 
IS40, |i. IDI i) BonlBch,(Phji)iologj,bd. •.;) Henle, (Allg. Anat. p. Bfifl:) "nd GulUver, 
(App, to Gorber'i GeDenl Anat.) Oh Ihe ijileat : Giesker, (Splenologie, Zurich, 1^35. 
quoted bf Henle ;) Mdller, (Arctiiv, IKil ;) ValenHD, (Uher den Veriauf der Blnt^ef. 
in dem Penis, Ac. Miiller's Archiv, 1B3S ;) Biscboff, (Miiller's Archlv, 1838 ;) Marcnf, 
[Diu. de funct. Uenls. IB38 ;) Boiuger;, Sui Is structure inllme de la rale, (Gazette 
Mnllcnle, Jniu II, lH4i, and Medical Gaxotle, August, IS4i! ;) Aiid Ibe enrlier works of 
Hewson, [leiulnger, Schmklt, and Meckel. Onlherenat eaptvUt: tiagfl, (Ueherdie 
Stmctur derNebennieren, Miiller's Archlv, IKJS ;J Bergmann, (Disi. deglandulU supra- 
rcMillbui, 1839;) Psppenfaeim, (VenDlschle Beobacht. Muller's Arcliit, ISIO;) and 
Berrei, (Unbet den zarten Bander Drusen, Oeater. Med. Jabr. ISIO.) On the tityreii 
and tiymut glandt : A. Cooper, (The Anatomy of the Tbyrons-gland ;) Derres, {/. c. in 
0«it«T. Jabrhuch ;) Hnllgsled, (Tbyml in bomine, 4c. qnolwl by Henle.) 

> The only two complete diracriptions are those of ^iiUer, (Enldeckting der bef det 
Krvcllon. . , wirksnmen Arterten, Archlv, 183S ;) sod Valentin, fUeber denVetlauf dei 
Iflulgvruw In dem Penli. Miilltsr's Aicbli, l»39,)witb a sab^nentnote by Miiller- 



, one of bundles of fibres, 

the midJle of the band or 

of layers is ususlly 

otber of each band there 



r directed in the longitudinnl itxia of the peni 
I like those of tendon ; Sth, the artery which oe 
I cord, and on the other side of which the sami 
I repeated, though leaa regularly, because on oni 
■e generally branches given off.' 
Thus far there is little question as to the structure of the true erectile tissue 
I the chief doubt is in regard to the mode in which the arteries pour their blooi 

< tbe reins. Miiller believes' that tbey have two distinct modes of 
I tioo; that aomo of them — the nutritive branches — form a common capiliary 
I network, which leads in tbe usual manner to tbe minute veins; but that, be- 
I Bides these, there are others, which he names helkine arteries. These, he says, 
orm branches about a line long and -^ of an inch thick, which usually proceed 
it right angles from the branches of the arteries within the bands and cords, 
I and hang loose, with blunt and curved or twisted, but not open, extremities 
] in the venous spnces. Through these the blood is. in erection, supposed to 
J be poured into the veins. Valentin,' on the other hand, maintains that the 
I appearance of the belicine arteries is artificially produced ; that, in cutting 
I across a collection of cellular spaces like those of the corpus cavernosum, many 
I of the bauds and cords which bound and traverse them must be divided ; and 
. since each of these coutnins in its interior a tortuous artery, it must, when 
I out nwaj from one of its connesiions and ttoated out in water, present the ap- 
I pearance of the end of an artery hanging loosely in a venous apace. Ho b«- 
I fieves, therefore, that the minutest branches of the arteries uf the penis, after 
various anastomoses, dilate, penetrate the flbrous tissue in which Ihcy are en- 
closed, and pass into thesmallest venous spaces, or (as it may be better expressed, 
in accordance with Berres' injections,) into a dense network of comparatively 
large veins, whose diameter is lour or fire times greater than that of the arteries, 
and the interspaces between which are formed by the intersecting fibrous bands 
and cords, in the substance of which the arteries run. 

In erection the blood, under nervous excitement, is poured more rapidly into 
the veins than it can be carried away through them: they are thus slowly dis- 
tended, but Dot completely, till by tbe tension and spasmodic contraction of the 
ischio-cavernosi and bulbo-cavemosi muscles, all the ven 
pressed and the circulation is still more obstructed. The 
fibrous tissue, are protected from compression, and can therefore 
carry blood after tbe passage through the veins has nearly ceased. 

' Thia deHcripllon Is drawn from the corpus cavernoeoni of the ass ; the 
enist, but are lesa ^llEcernible, in that of mnn. 

' And he la, In general, confirmed hy Krause, (Vermlschte Beobachl, Miill. Arobiv, 
IS31 ;) HjtO, (Oester. Jahr. IB38, bil. xlx. ;) and Erdl, (Miiller'a Archiv, !B41.> But 
«ee on their ohaervBtionB, Valentin, HeijerLurium, 1841, 

' Hia obBenBlionsnteconfirmad by i!ertea,(Ueberden zarlenBauder Dnisen, Oeater. 
Jahrb. bd. xxiU) 



s trunks ai 

I, running it 



I 






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